Compositions and methods of promoting organic photocatalysis

ABSTRACT

The invention provides novel compounds and methods that are useful in promoting reactions that proceed through an oxidative quenching pathway. In certain embodiments, the reactions comprise atom transfer radical polymerization.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of, and claimspriority to, PCT International Application No. PCT/US2016/058245, filedOct. 21, 2016, designating the United States and published in English aspublication WO 2017/070560 on Apr. 27, 2017, which claims priority under35 U.S.C. § 119(e) to U.S. Provisional Applications No. 62/245,804,filed Oct. 23, 2015, No. 62/316,036, filed Mar. 31, 2016, and No.62/378,563, filed Aug. 23, 2016, all of which applications areincorporated herein by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under grant numberDE-AR0000683 awarded by the Advanced Research Projects Agency-Energy(Department of Energy) and grant number R35GM119702 awarded by theNational Institute of General Medical Sciences (National Institutes ofHealth). The government has certain rights in the invention.

BACKGROUND OF THE INVENTION

Atom transfer radical polymerization (ATRP) is one of the most powerfulmethodologies for precision polymer synthesis, and is considered to bethe most important advancement in polymer synthesis in the last 50years. Strict control over the equilibrium between a dormant alkylhalide and active propagating radical dictates a low concentration ofradicals and minimizes bimolecular termination to achieve controlledpolymerization. ATRP has historically relied on transition metalcatalysts to mediate this equilibrium and polymerize monomers withdiverse functionality into macromolecules with controlled molecularweight (MW), low MW dispersity (Ð), defined chemical composition, andcomplex architecture.

The caveat of traditional ATRP is that the transition metal catalystspresent purification challenges for the polymer product and restricttheir use in biomedical and electronic applications. Despite significantadvancements to lower catalyst loading and improve purificationtechniques, organocatalyzed methods remain highly desirable. Forexample, organocatalyzed variants of ATRP using alkyl iodide initiatorshave been established, although they are not a broadly applicablereplacement for metal-catalyzed ATRP. Considerable motivation thusexists for developing catalysts that mediate organocatalyzed ATRP(O-ATRP).

Photoredox catalysis is considered as a “green” process by introducingthe opportunity to perform reactions under mild conditions, includingambient temperatures and using light. Upon irradiation and access of anexcited state, a photocatalyst becomes both a stronger oxidant andreductant. This excited state molecule can then be exploited as acatalyst, through either a reductive or oxidative quenching pathway. Thereductive quenching pathway commonly employs sacrificial electrondonors, while the oxidative quenching pathway allows for direct electrontransfer from the excited state photocatalyst. The reductive quenchingpathway can be less desirable due to the need for a sacrificial electrondonor, which can introduce undesirable decomposition pathways. Theoxidative quenching pathway avoids these complications, but is lesscommonly used. Organic molecules are desirable photocatalysts becausethey are typically less expensive and eliminate the use of metalcatalysts. However, organic photocatalysts that can mediate catalytictransformations through an oxidative quenching pathway are less common.

There is thus a need in the art for novel methods of promoting reactionsusing less expensive organic photocatalysts capable of performingoxidative and/or reductive steps. The present invention fulfills thisneed.

BRIEF SUMMARY OF THE INVENTION

The invention provides a method of promoting reaction of at least onereagent, wherein the reaction comprises a quenching step. The inventionfurther provides certain organic compounds, which are useful within themethods of the present invention.

In certain embodiments, the quenching step is oxidative. In otherembodiments, the quenching step is reductive.

In certain embodiments, the method comprises irradiating the at leastone reagent in the presence of an organic compound with an excited-statereduction potential that is equal to or more negative than about −1.0 Vvs. SCE.

In certain embodiments, the excited state comprises a singlet or tripletexcited state. In other embodiments, the excited-state reductionpotential is equal to or more negative than one selected from the groupconsisting of about −2.4 V vs. SCE, −2.3 V vs. SCE, about −2.2 V vs.SCE, about −2.1 V vs. SCE, about −2.0 V vs. SCE, about −1.9 V vs. SCE,about −1.8 V vs. SCE, about −1.7 V vs. SCE, about −1.6 V vs. SCE, about−1.5 V vs. SCE, about −1.4 V vs. SCE, about −1.3 V vs. SCE, about −1.2 Vvs. SCE, and about −1.1 V vs. SCE. In yet other embodiments, thereaction comprises at least one selected from the group consisting ofatom transfer radical addition/polymerization, dehalogenation,cycloaddition, cyclization, dimerization, coupling, reduction,ring-opening, alkylation, arylation, oxygenation, energy transfer, andradical addition. In yet other embodiments, the reaction comprises atomtransfer radical addition/polymerization. In yet other embodiments, theat least one reagent comprises a (meth)acrylate and an organic halide.In yet other embodiments, the organic halide comprises an α-halo ester.In yet other embodiments, the reaction is essentially free of a metal ormetalloid. In yet other embodiments, the polymerization reaction yieldsa polymer of dispersity equal to or lower than a value selected from thegroup consisting of about 1.13, about 1.20, and about 1.31. In yet otherembodiments, the polymerization reaction yields a polymer of dispersityequal to or lower than about 2.0. In yet other embodiments, thepolymerization reaction yields a polymer of tunable molecular weight.

In certain embodiments, the radiation comprises visible light. In otherembodiments, the radiation comprises sunlight natural light source. Inyet other embodiments, radiation comprises radiation provided by a LED.In yet other embodiments, the radiation comprises ultraviolet orinfrared light.

In certain embodiments, the organic compound is at least one selectedfrom the group consisting of:

and, wherein

each occurrence of R is independently selected from the group consistingof H, C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substituted phenyl, —OH,—O(C₁-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl);

each occurrence of R₁ is independently selected from phenyl, 1-naphthyland 2-naphthyl, each of which is independently substituted with at leastone R;

each occurrence of R₂ and R₃ is independently selected from phenyl and(4-phenyl)-phenyl, each of which is independently substituted with atleast one R;

or a salt or solvate thereof.

In certain embodiments, each occurrence of R is independently selectedfrom the group consisting of optionally substituted phenyl, C₁-C₆haloalkyl, —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl), —C(═O)O-phenyl,—C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂, —S(O)₂NH(C₁-C₆ alkyl),—S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆alkyl), —S(O)(phenyl), and —S(O)₂(phenyl). In other embodiments, atleast one occurrence of R is optionally substituted phenyl, —CF₃ or—NO₂. In yet other embodiments, R₂ and R₃ are identical. In yet otherembodiments, if two R₁ groups are present, they are identical.

In certain embodiments, the compound is selected from the groupconsisting of

or a salt or solvate thereof.

In certain embodiments, the compound is selected from the groupconsisting of:

wherein:

each occurrence of R is independently selected from the group consistingof H, C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substituted phenyl, —OH,—O(C₁-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl);

each occurrence of R₁ is independently selected from phenyl, 1-naphthyland 2-naphthyl, each of which is independently substituted with at leastone R; and

each occurrence of R₂ and R₃ is independently selected from phenyl and4-phenyl-phenyl, each of which is independently substituted with atleast one R,

or a salt or solvate thereof.

In various embodiments, the organic compound is at least one selectedfrom the group consisting of:

wherein:

each occurrence of R is independently selected from the group consistingof H, C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substituted phenyl, —OH,—O(C₁-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl);

each occurrence of R₁ is independently selected from the groupconsisting of phenyl, 1-naphthyl and 2-naphthyl, each of which isindependently substituted with at least one R; and

each occurrence of R₂ and R₃ is independently selected from phenyl and4-phenyl-phenyl, each of which is independently substituted with atleast one R; and

each occurrence of R₃, R₄, R₅, and R₆ is independently selected from thegroup consisting of phenyl, 4-phenyl-phenyl, 1-naphthryl, 2-naphthryl,triphenylamine, phenanthrenyl, and pyrenyl, each of which isindependently substituted with at least one R;

or a salt or solvate thereof.

In certain embodiments, R₃ and R₅ are H. In other embodiments, R₄ and R₆are H. In yet other embodiments, R₃═R₅. In yet other embodiments, R₄═R₆.In yet other embodiments, R₃ is H and R₅ is not H. In other embodiments,R₄ is H and R₆ is not H. In yet other embodiments, R₃ and R₅ are not H.In yet other embodiments, R₄ and R₆ are not H.

In various embodiments, the organic compound is at least one selectedfrom the group consisting of:

or a salt or solvate thereof.

In another aspect, the invention provides a method of promoting reactionof at least one reagent, wherein the reaction comprises an oxidative orreductive quenching step, wherein the method comprises irradiating theat least one reagent in the presence of an organic compound with anexcited-state reduction potential that is equal to or more negative thanabout −1.0 V vs. SCE, or a salt or radical of an organic compound thatpossesses an excited-state reduction potential that is equal to or morenegative than about −1.0 V vs. SCE.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there are depicted in thedrawings certain embodiments of the invention. However, the invention isnot limited to the precise arrangements and instrumentalities of theembodiments depicted in the drawings.

FIGS. 1A-1C illustrates aspects of photocatalysis contemplated withinthe invention. FIG. 1A: Polymerization of methyl methacrylate towell-defined polymers using photoredox O-ATRP. FIG. 1B: Diphenyldihydrophenazine photocatalysts contemplated within the invention. FIG.1C: A non-limiting proposed general mechanism for ATRP mediated by a PCvia photoexcitation, intersystem crossing to the triplet state, ET toform the radical cation doublet and back ET to regenerate PC andterminate polymerization. The table at the bottom illustrates anon-limiting list of the computed redox properties of the diphenyldihydrophenazine photocatalysts.

FIGS. 2A-2D illustrates non-limiting results obtained using methods ofthe invention. FIG. 2A: Plot of molecular weight as a function ofmonomer conversion. FIG. 2B: Plot of dispersity as a function of monomerconversion. FIG. 2C: Plot of monomer conversion during irradiation(light bulb) and dark (gray) sequences. FIG. 2D: Plot of M_(n)(left-axis) and Ð (right-axis) as a function of monomer conversion forthe pulsed-light irradiation experiment. Conditions: 1.0 mL DMA, 1.0 mLMMA, [MMA]:[EBP]:[3]=[1000]:[10]:[1].

FIG. 3 is a scheme illustrating: left—chain-extension from a PMMAmacro-initiator (black) to produce block polymers with MMA (green),benzyl methacrylate (blue), and butyl acrylate (red); right—gelpermeation chromatography (GPC) traces of each polymer (the maximums ofthe curves are, in increasing mL values (left to right), blue, green,red and black.

FIG. 4 is a scheme illustrating triplet state frontier orbitals ofdiphenyl dihydrophenazine photocatalysts contemplated within theinvention. Top figures show the higher-lying singly occupied molecularorbital (SOMO) and bottom figures the low-lying SOMO. Phenylfunctionalization with electron withdrawing groups (CF₃ and CN)localizes the high-lying SOMO on the phenyl group.

FIG. 5 is an exemplary photograph of the general reaction setup forpolymerizations using LED irradiation.

FIG. 6 is an image of a reaction of the invention being run in naturalsunlight.

FIGS. 7A-7F are a set of graphs illustrating UV-Vis spectra of catalysts1 (FIG. 7A), 2 (FIG. 7B), 3 (FIG. 7C), 4 (FIG. 7D), 5 (FIG. 7E), and 6(FIG. 7F) at 0.15 mM in DMF.

FIG. 8A illustrates GPC trace of runs 11 (green), 12 (blue), 13 (red),and 14 (black) (in increasing order to maximum elution volume:green<blue<red<black), Table 2. FIG. 8B illustrates GPC trace of runs 10(purple) 9 (green), 3 (blue), 8 (red), and 7 (black) (in increasingorder to maximum elution volume: purple<green<blue<red<black), Table 2.

FIG. 9 is a GPC trace showing the results of the synthesis ofPMMA-b-PMMA; the polymer produced after 12 hours (black; right curve)and the polymer produced after additional monomer and 6 hours ofirradiation (blue; left curve).

FIG. 10 is a GPC trace showing the results of the synthesis ofPMMA-b-PMMA with a dark resting period: the polymer produced after 8hours (red), the polymer produced after the dark period (black), and thepolymer produced after additional monomer and irradiation 8 hours of(blue) (in increasing order to maximum elution volume: blue<red˜black).

FIG. 11 is a GPC trace showing the results of the synthesis ofPMMA-b-PBA with a dark resting period: polymer produced after 8 hours(red), the polymer produced after the dark period (black), and thepolymer produced after additional monomer and 8 hours of irradiation(blue) (in increasing order to maximum elution volume: blue<red˜black).

FIG. 12 is a GPC trace showing the results of the synthesis ofPMMA-b-PBnMA with a dark resting period: the polymer produced after 8hours (red), the polymer produced after the dark period (black), and thepolymer produced after additional monomer 8 hours of irradiation (blue)(in increasing order to maximum elution volume: blue<red˜black).

FIG. 13 is a graph illustrating a cyclic voltammetry (CV) of EBP onglassy carbon electrode in acetonitrile (0.10 M Bu₄NClO₄ electrolyte).Scan rate=100 mV/s. Onset of EBP reduction at ˜−0.8 V vs. SCE. CV wasperformed using saturated Ag/AgCl reference electrode, and was convertedto vs. SCE by subtracting 0.043 V. Although the onset of reductionmeasured here is consistent with the calculated E⁰ (EBP/EBP^(⋅−)) of−0.74 V vs. SCE, an actual E⁰ is determined using saturated solute andstandard conditions that produce a reversible CV.

FIG. 14 is a scheme illustrating non-limiting mechanisms of photoredoxmediated polymerizations proceeding through a reductive or oxidativequenching pathway.

FIG. 15 is a schematic illustration of certain compounds contemplatedwithin the invention.

FIG. 16 is a graph illustrating polymer molecular weight and dispersityvs conversion for 3.

FIG. 17 is a graph illustrating first order kinetic plot of monomerconversion vs time for coronene as a photocatalyst.

FIGS. 18-19 illustrate experimental results obtained within theinvention.

FIG. 20A illustrates (Top) Computed and experimentally measuredproperties of 5 and 6. (Bottom) Structures of 5, 6, and MBP (methyl2-bromopropionate). FIG. 20B illustrates triplet state frontier orbitalsof 5 and 6. Top figures show the higher-lying SOMO and bottom figuresthe low-lying SOMO. FIG. 20C illustrates plot of Mn and Ð vs. monomerconversion for the polymerization of MMA. FIG. 20D illustrates plot ofmonomer conversion vs. time. FIG. 20E illustrates plot of Mn and Ð(filled symbols from after irradiation and empty symbols from after darkperiod) vs. monomer conversion using 6 as the PC during pulsed lightirradiation with white LEDs.

FIG. 21 illustrates emission spectra of catalysts 1 (A), 2 (B), 3 (C), 4(D), 5 (E), and 6 (F) in DMF.

FIGS. 22A-22F illustrate cyclic voltammograins (vs. Ag/AgNO₃) ofcatalysts 1 (FIG. 22A), 2 (FIG. 22B), 3 (FIG. 22C), 4 (FIG. 22D), 5(FIG. 22E), and 6 (FIG. 22F) in MeCN.

FIG. 23A illustrates O-ATRP mediated by organic PCs using alkyl bromideinitiators and aryl phenoxazines. FIG. 23B illustrates additionalorganic PCs. FIG. 23C illustrates non-limiting general photoredoxcatalytic cycle of O-ATRP.

FIG. 24 illustrates geometric reorganization energies and reductionpotentials (vs SCE) for 10-phenylphenoxazine, diphenyl dihydrophenazine,and 10-phenylphenothiazine (bottom) transitioning from the ³PC* to²PC^(⋅+) to ¹PC species involved in an illustrative mechanism forphotoredox O-ATRP.

FIG. 25A illustrates N-aryl phenoxazines along with computed tripletstate reduction potentials. FIG. 25B illustrates computed triplet stateSOMOs of phenoxazine derivatives.

FIG. 26, which relates to Example 7, illustrates plots of molecularweight (M_(n), blue) and dispersity (Ð, orange) as a function of monomerconversion for the polymerization of MMA catalyzed by 3 (Panel A) and 4(Panel B). Plots of conversion vs time using 3 (Panel C) or 4 (Panel E)(irradiation in white and dark periods in gray) and plots of molecularweight (M_(n), blue) and dispersity (Ð, orange; marked as “*”) as afunction of MMA conversion using a pulsed-irradiation sequence and PC 3(Panel D) or 4 (Panel F) (filled markers are data directly afterirradiation while open markers are data directly after the dark period).Conditions for all plots: [MMA]:[DBMM]:[PC]=[1000]:[10]:[1]; 9.35 μmolesPC, 1.00 mL dimethylacetamide, and irradiated with UV-light.

FIG. 27, which relates to Example 7, illustrates chain extensionpolymerizations from a PMMA macroinitiator (A) with MMA (B), IDMA (C),BMA (D), BnMA (E). Gel permeation chromatography traces of the polymersdepicted by the chemical structures with corresponding color schemes(F).

FIGS. 28A-28B illustrate X-ray crystal structures of 1-naphthalenesubstituted planar phenoxazine (FIG. 28A) and bent phenothiazine (FIG.28B). Hydrogen atoms omitted for clarity. Thermal ellipsoids are drawnat the 50% probability level (C gray, N blue, O red, S yellow).

FIGS. 29A-29C illustrate ESP mapped electron density of ³PC* and ¹PC of1-naphthalene substituted phenoxazine (FIG. 29A), dihydrophenazine (FIG.29B), and phenothiazine (FIG. 29C).

FIGS. 30A-30D, which relate to Example 7, illustrate properties of PC 5.FIG. 30A: Structure, computed triplet excited state reduction potential,and ESP mapped electron density of ³PC* 5. FIG. 30B: Computed tripletstate SOMOs of PC 5. FIG. 30C: Plot of M_(n) and Ð as a function ofmonomer conversion for the polymerization of MMA by PC 5;[MMA]:[DBMM]:[5]=[1000]:[10]:[1]; 9.35 μmoles PC, 1.00 mLdimethylacetamide, and irradiated with white LEDs (orange, signaled with“*”). FIG. 30D: UV-vis spectrum of PC 5 and 1-naphthalene functionalizedphenoxazine, dihydrophenazine, and phenothiazine, with color codedstructures, and extinction coefficients at their respective λ_(max) withthe visible absorbance spectrum highlighted in white.

FIG. 31 illustrates a photograph of the reaction setup for O-ATRP usingUV irradiation.

FIG. 32, which relates to Example 7, illustrates UV-vis absorptionspectrums of the phenoxazine photocatalysts. PC 1-4 were taken at 0.20mM and PC 5 was taken at 0.06 mM. Solvent=DMA. Path length=1 cm.

FIGS. 33A-33E, which relate to Example 7, illustrate UV-vis absorptionof the phenoxazine catalysts taken at different concentrations in DMA.Path length=1 cm.

FIG. 34, which relates to Example 7, illustrates a plot of thenormalized emission spectrums of the phenoxazine photocatalysts in DMA.PC 1-4 were irradiated with 320 nm light while PC 5 was irradiated with380 nm light.

FIGS. 35A-35B illustrate cyclic voltammograms of the phenoxazinephotocatalysts performed in a 3-compartment electrochemical cell.Reference electrode: Ag/AgNO₃ (0.01M) in MeCN; electrolyte: 0.1 MNBu₄PF₆; scan rate: 0.10 V/s. DMA is used as the solvent in the workingelectrode compartment for (b)-(e) while MeCN is used as the solvent in(a). Platinum is used as both the working and counter electrodes.

FIG. 36, which relates to Example 7, illustrates gel permeation tracesof PMMA produced using 3 (left) and 4 (right) reported in Table 9. Colorscheme corresponds to: (left plot) run 5 (light blue), run 6 (gray), run7 (orange), run 8 (red), run 9 (green), run 10 (blue), run 11 (purple),run 12 (black); (right plot) run 13 (light blue), run 14 (orange), run15 (gray), run 16 (red), run 17 (green), run 18 (blue), run 19 (purple),run 20 (black). Curve colors are in both plots, from left to right:blue, green, red, gray, orange, purple, black and light blue.

FIGS. 37A-37B, which relate to Example 7, illustrate plots of numberaverage molecular weight (blue) and dispersity (orange; marked with “*”)as a function of monomer conversion in the polymerization of methylmethacrylate catalyzed by 1-napthylene-10-phenoxazine (FIG. 37A) and1-napthylene-10-phenothiazine (FIG. 37B). Conditions:[MMA]:[DBMM]:[PC]=[1000]:[10]:[1]; 9.35 μmoles PC, 1.00 mLdimethylacetamide, and irradiated with 365 nm light.

FIG. 38 depicts radical addition reactions according to embodiments ofthe invention, comprising radical trifluoromethylations on alkenes,five-membered heteroarenes, arenes, and cross-addition on alkenes.

FIG. 39 depicts coupling reactions according to embodiments of theinvention, comprising dual organic photoredox and nickel catalyzed C—Ncross-coupling reaction scope.

FIG. 40 depicts dual organic photoredox and nickel catalyzed C—Scross-coupling scope. Data reported as isolated yields. For all of FIGS.38-40, values in parentheses are the ratio of Z:E:b-hydride eliminationproduct. [a] Reaction was also conducted using sunlight for 1 week (67%yield for trifluoromethylation, 83% yield for C—N coupling, 94% yieldfor C—S coupling). [b] CF₃CF₂I was used instead of CF₃I. [c] Reactiontime 6 h. [d] Reaction was also conducted on a larger 10 mmol scale (73%yield for trifluoromethylation, 53% yield for C—N coupling, 98% yieldfor C—S coupling). [e] Reaction was also conducted at reduced catalystloading of 0.25 mol %, instead of standard 1.0 mol % (69% yield fortrifluoromethylation after 24 h). [f] Performed without HCOOK. [g]Reaction performed with 10 mol % pyrrolidine as the ligand and reducednickel loading to 1.0 mol %. [h] Reaction catalyzed by PC 4. [i]Reaction catalyzed by PC 3.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to the unexpected discovery of that certainorganic compounds can be used as photocatalysts in reactions thatproceed via an oxidative and/or reductive quenching pathway, such as butnot limited to atom transfer polymerization reactions. In certainembodiments, the organic compounds of the invention are strongreductants in the excited state. In other embodiments, the methods ofthe invention do not utilize transition metal catalysts and thus areessentially metal-free.

The organic compounds of present invention may be used not only in atomtransfer radical polymerization, but to reactions such as halogenations,cycloadditions, cyclizations, dimerizations, couplings (carbon-carbonbond formation, carbon-nitrogen bond formation, carbon-oxygen bondformation, carbon-sulfur bond formation and carbon-phosphorus bondformation), reductions, ring-opening reaction, alkylations, arylations,oxygenations, radical additions, among others. Such reactions can beconducted under batch conditions, flow conditions, or on surfaces. Incertain non-limiting, embodiments, the ability to control reactivitywith light allows the opportunity for spatial and temporal control. Inother non-limiting embodiments, the use of these catalysts forphotolithography allows for versatile polymerizations orfunctionalization from/to surfaces.

In certain aspects, the present disclosure relates to the use of O-ATRPto synthesize polymers. In certain embodiments, the methods of theinvention provide similar precision as traditional ATRP, but instead usevisible light photocatalysts (PCs) to realize energy efficient,“greener” polymerization methods. Visible-light photocatalysis allowsfor harnessing solar energy to mediate chemical transformations undermild conditions.

FIG. 1C illustrates a non-limiting mechanism of a photoredox O-ATRP,wherein a PC reversibly activates an alkyl bromide. In addition to theneed for a strong reduction potential for the excited state PC, adelicate interplay must be balanced between the stability of its cationradical PC^(+⋅) and its oxidation potential relative to the propagatingradical to yield a controlled radical polymerization.

In one aspect, 5,10-diaryl-5,10-dihydrophenazines can be utilized as aclass of PCs for O-ATRP (FIG. 1B). The phenazine core is shared byseveral biologically relevant molecules that serve as redox-activeantibiotics, while synthetic derivatives have drawn interest in organicphotovoltaics and organic ferromagnets. In certain embodiments, anappropriate union between the excited-state reduction potential)(E⁰ andthe stability of the resulting radical cation PC^(+⋅) allows for theproduction of polymers with controlled MW and low Ð. As such, electrondonating (OMe, 1), neutral (H, 2), and withdrawing (CF₃, 3 and CN, 4)moieties on the N-phenyl substituents were investigated.

Density Functional Theory (DFT) was used to calculate the reductionpotentials, E⁰, of the triplet excited state photocatalysts, initiator,and propagating radicals. 2 possesses a triplet excited-state reductionpotential of E⁰ (³PC*/PC^(+⋅))=−2.34 V vs. SCE. Functionalization of thephenyl substituents with an electron donating group OMe (1) strengthenedthe reduction potential to −2.36 V, while introduction of electronwithdrawing groups (EWGs) weakened the reduction potential to −2.24 and−2.06 V for 3 and 4, respectively. The triplet excited states of thesePCs were all strongly reducing with respect to 1e⁻ transfer to ethylα-bromophenylacetate (EBP). E⁰⁽EBP/EBP^(−⋅)) was calculated to be −0.74V vs. SCE, consistent with the cyclic voltammetry results, which showedthat the onset of EBP reduction occurs at ˜−0.8 V vs. SCE (FIG. 13).These reduction potentials are significantly more reducing than classicmetal PCs, including polypyridyl iridium complexes (E^(0*) as negativeas −1.73 V vs. SCE) that have been used in photomediated ATRP. However,iridium PCs are expensive, do not address the problem of metalcontamination, and have only been demonstrated to produce polymers withÐ as low as 1.19.

The reducing power of these PCs exhibited by their negativeE⁰(³PC*/PC^(+⋅))s arises from a distinct combination of their hightriplet state energies (˜2.2-2.4 eV) and the formation of relativelystable radical cations [E⁰(PC^(+⋅)/PC)=˜−0.1-0.2 V] upon theiroxidation. Furthermore, these radical cations are also sufficientlyoxidizing to deactivate the propagating chains. E⁰s for propagatingradicals with n monomer repeat unit(s) bound to EBP ofE⁰([EBP-MMA_(n)]/[EBP-MMA_(n)]^(−⋅)) were computed to be −0.74, −0.86,and −0.71 V, for n=0, 1 and 2, respectively. These E⁰s were sufficientlynegative with respect to oxidization by the radical cations to driveradical deactivation and regeneration of the PC to complete thephotocatalytic cycle.

The series of target PCs were synthesized in two steps from commercialreagents in good yields. Under otherwise identical conditions, all ofthe PCs were tested in the polymerization of methyl methacrylate (MMA),using EBP as the initiator and white LEDs for irradiation indimethylacetamide (Table 2, runs 1-4). All four PCs proved effective inpolymerization after 8 hours of irradiation, with the PCs bearing EWGsexhibiting the best catalytic performance. PC 3 allowed for theproduction of polymers with a combination of not only the lowestdispersity (Ð=1.17), but also the highest initiator efficiency(I*=65.9%). This polymerization could even be driven with sunlight toproduce polymethyl methacrylate (PMMA) with an impressively lowdispersity of Ð=1.10 (Mw=7.54 kDa).

3 was further characterized herein (Table 1). To examine thepolymerization in detail, time-point-aliquots were taken duringpolymerization to monitor the MW and Ð progression as a function ofmonomer conversion (FIGS. 2A-2B). The control provided by 3 wasevidenced by the linear increase in polymer MW and low Ð throughout thecourse of polymerization. Furthermore, temporal control was realized byemploying a pulsed-irradiation sequence (FIG. 2C). Polymerization wasonly observed during irradiation pulses, paused during dark periods, andthe MW steadily increased with continued irradiation while maintaininglow Ð (FIG. 2D).

To investigate the potential for modulation of the polymer MW, theeffect of adjusting the initiator ratio was tested (Table 1, runs 3-6).The M_(w) of the resulting PMMA was modulated from 7.12 to 85.5 kDa.High EBP ratios resulted in controlled polymerizations and lowdispersities (Ð=1.26-1.17), and despite the moderate loss of precisecontrol over the polymerization at low EBP ratios (Ð=1.54), high MWpolymer was produced achieving high initiator efficiency (Mw=85.5 kDa,I*=86.3%). Alternatively, adjusting the monomer ratio regulated polymerMW while also maintaining low Ð (Table 1, runs 7-10). Efficient controlover the polymerization by 3 is highlighted by the consistently high I*and low Ð achieved over broad reaction conditions to produce polymerswith tunable MWs through varying initiator or monomer ratios.

Traditional ATRP allows for the synthesis of well-defined blockcopolymers. The reversible-deactivation mechanism enforced in ATRPcontinuously reinstalls the Br chain-end group onto the polymer andthus, isolated polymers can be used to reinitiate polymerization. Tofurther support that this polymerization operates via an O-ATRPmechanism, a series of block polymerizations were performed.

In one aspect, after initial polymerization of MMA proceeded for 12 h,more MMA was added to the reaction. GPC analysis revealed that the MW ofthe resulting polymer quantitatively increased (FIG. 9). In anotheraspect, after polymerization of MMA was allowed to proceed for 8 h, thereaction mixture was placed in the dark for 8 h and subsequently moreMMA was added. This resulted in no polymerization during the darkperiod, while the subsequent addition of MMA and further illuminationresulted in continued and controlled polymer chain growth (FIG. 10). Inyet another aspect, an isolated polymer (Table 1, run 7) wasreintroduced to polymerization conditions by adding monomer, catalyst,solvent, and light, and served as a macro-initiator for the synthesis ofblock polymers. This chain-extension proved successful with MMA, benzylmethacrylate, and butyl acrylate (FIG. 3). The chain-extensionpolymerization from an isolated polymer produced from thispolymerization method strongly supports that this method proceedsthrough the ATRP mechanism.

DFT calculations were performed to gain insight into the differences inthe performances of the PCs, all of which possess similarE⁰(³PC*/PC^(+⋅))s and E⁰(PC^(+⋅)/PC)s that are sufficiently reducing andoxidizing, respectively, to drive the photocatalytic cycle. Withoutwishing to be limited by any theory, the performances of 4 and, inparticular, 3 can be qualitatively different from that of 1 and 2 andresult from a more complex effect.

Inspection of the triplet state frontier orbitals reveals qualitativedifferences in these PCs (FIG. 4). The low-lying Singly OccupiedMolecular Orbital (SOMO) of all the PCs are similar, with the electronlocalized over the phenazine π system. Similarly, for PCs 1 (OMe) and 2(H), the high-lying SOMO is also localized on the phenazine rings. Incontrast, for 3 (CF₃) and 4 (CN) the high-lying SOMO, occupied by thereducing triplet e−, resides on the phenyl ring(s). Without wishing tobe limited by any theory, the CF₃ and CN EWGs stabilize the π* orbitalslocalized on the phenyl rings relative to the π* orbital that is thehigh-lying SOMO of 1 and 2. This reorders the energies of the π*orbitals such that a π* orbital localized on the phenyls becomes thehigh-lying SOMO of 3 and 4, although the low-lying SOMO localized on thephenazine moiety remains singly occupied. Thus, the reducing e− of thePC triplet excited state (³PC*) of 3 and 4 is localized on the phenylrings.

Furthermore, a comparison of 3 to 4 elucidates another significantdistinction. For 3, the high-lying SOMO is localized on one of thephenyl rings, while in 4 the reducing e− is delocalized over both phenylrings. One of the C—F bonds, containing the high-lying SOMO of 3, islengthened from ˜1.35 Å to 1.40 Å, indicating partial localization ofelectron density in this C—F's antibonding orbital. Thus, 3 and 4 differfrom 1 and 2 in that the triplet electrons of 3 and 4 reside on both thephenazine and the phenyl ring(s) and are thus spatially separated.

As demonstrated herein, a series of diphenyl dihydrophenazines weresynthesized and introduced as organic PCs in O-ATRP to efficientlypolymerize MMA and other monomers to well-defined polymers. Firstprinciples calculations inspired the discovery of these PCs andinitiated examination of PCs such as 3. The catalysts studied herein canbe used in the synthesis of polymers using O-ATRP.

TABLE 1 Results for the Organocatalyzed Atom Transfe RadicalPolymerization of Methyl Methacrylate Catalyzed by 3 Using White LEDs orSunlight^(a). Run DMA Time Conv. M_(w) Ð No. [MMA]:[EBP]:[3] (mL) (h)(%)^(c) (kDa) (M_(w)/M_(n))  1 [1000]:[10]:[1] 1.0 8 98.4 17.9 1.17 2^(a) [1000]:[10]:[1] 1.0 7 33.8 7.54 1.10  3 [1000]:[20]:[1] 1.0 878.9 7.12 1.18  4 [1000]:[15]:[1] 1.0 8 67.8 8.74 1.18  5 [1000]:[5]:[1]1.0 8 86.9 37.3 1.26  6 [1000]:[2]:[1] 1.0 8 95.2 85.5 1.54  7[5000]:[12]:[1] 5.0 6.5 46.5 43.4 1.29  8 [2000]:[10]:[1] 2.0 6.5 57.119.5 1.31  9 [750]:[10]:[1] 1.25 6.5 53.2 7.75 1.30 10 [500]:[10]:[1]0.75 6.5 64.0 4.83 1.12

TABLE 2 Results for the Organocatalyzed Atom Transfer RadicalPolymerization of Methyl Methacrylate. Run DMA Time Conv. M_(w) M_(n) ÐM_(n) (theo) I* No. PC [MMA]:[EBP]:[PC] (mL) (h) (%)^(c) (kDa)^(d)(kDa)^(d) (M_(w)/M_(n))^(d) (kDa)^(e) (%)^(f)  1 1 [1000]:[10]:[1] 1.0 869.6 36.3 24.7 1.47 7.21 29.2  2 2 [1000]:[10]:[1] 1.0 8 85.9 18.4 11.91.55 8.84 74.5  3 3 [1000]:[10]:[1] 1.0 8 98.4 17.9 15.3 1.17 10.1 65.9 4 4 [1000]:[10]:[1] 1.0 8 73.5 21.4 16.1 1.33 7.60 47.2  5^(b) 3[1000]:[10]:[1] 1.0 7 33.8 7.54 6.85 1.10 3.63 52.9  6^(b) 4[1000]:[10]:[1] 1.0 7 36.7 9.63 7.47 1.29 3.92 52.5  7 3 [1000]:[20]:[1]1.0 8 78.9 7.12 6.03 1.18 4.19 69.5  8 3 [1000]:[15]:[1] 1.0 8 67.8 8.747.41 1.18 4.77 64.3  9 3 [1000]:[5]:[1] 1.0 8 86.9 37.3 29.6 1.26 17.659.6 10 3 [1000]:[2]:[1] 1.0 8 95.2 85.5 55.5 1.54 47.9 86.3 11 3[5000]:[12]:[1] 5.0 6.5 46.5 43.4 33.6 1.29 19.6 58.5 12 3[2000]:[10]:[1] 2.0 6.5 57.1 19.5 14.9 1.31 11.7 78.4 13 3[750]:[10]:[1] 1.25 6.5 53.2 7.75 5.96 1.30 4.24 71.1 14 3[500]:[10]:[1] 0.75 6.5 64.0 4.83 4.31 1.12 3.45 79.9^(a)Polymerizations were performed in dimethylacetamide using 9.35 μmolof PC and irradiated using white LED lights, except runs 5 and 6, whichwere irradiated with sunlight^(b). ^(c)Measured by ¹H NMR. ^(d)Measuredby gel-permeation chromatography coupled with light-scattering.^(e)Theoretical number-average molecular weight, determined by themonomer to initiator ratio, the monomer conversion, and molecular weightof EBP. ^(f)Calculated from the ratio of the theoretically predicted toexperimentally observed number-average molecular weights. A survey ofinitiators commonly employed in traditional metal-catalyzed ATRP inconjunction with 6 (Table 3, run 11 and Table 4, runs 9-12) revealedthat methyl 2-bromopropionate (MBP) provided the best overall resultsfor the polymerization of MMA (M_(w) = 10.6 kDa; Ð = 1.28; I* = 88.1%).Furthermore, temporal control was realized by employing apulsed-irradiation sequence (FIGS. 20D-26E). Polymerization was observedonly during irradiation, paused during dark periods, and the MW steadilyincreased with continued irradiation while producing a polymer with alow Ð of 1.17. Finally, efficient control over the polymerization by 6is highlighted by the consistently high I* achieved over broad reactionconditions to produce polymers with tunable MWs through varyinginitiator (Runs 11-14) or monomer (Runs 15-17) ratios.

TABLE 3 Results for the Organocatalyzed Atom Transfer RadicalPolymerization of Methyl Methacrylate Catalyzed by 6 Using White LEDs. ÐI* Run Time Conv. M_(w) (M_(w)/ (M_(n(theo))/ No. [MMA]:[MBP]:[6] (h)(%) (kDa) M_(n)) M_(n(exp))) 11 [1000]:[10]:[1] 8 71.7 10.6 1.28 88.1 12[1000]:[20]:[1] 8 73.1 5.24 1.29 94.5 13 [1000]:[15]:[1] 8 70.8 7.521.36 88.5 14 [5000]:[10]:[1] 8 69.5 46.9 1.32 98.7 15 [2500]:[10]:[1] 864.5 21.9 1.34 99.3 16 [750]:[10]:[1] 8 69.0 6.93 1.23 94.7 17[500]:[10]:[1] 8 76.4 5.74 1.39 95.7

TABLE 4 Computed photophysical properties of photocatalysts 1-6. Tripletenergy E⁰ (PC^(•+)/³PC*) E⁰ (PC^(•+)/PC) PC (eV) (V vs SCE) (V vs SCE) 12.31 −2.36 −0.05 2 2.34 −2.34 0.00 3 2.37 −2.24 0.13 4 2.21 −2.06 0.16 52.10 −2.20 −0.02 6 2.15 −2.12 0.02

In conclusion, a series of computationally designed diaryldihydrophenazines were synthesized and investigated as organic PCs inO-ATRP to efficiently polymerize MMA and other monomers to well-definedpolymers, synthesizing polymers with dispersity as low as 1.03 anddemonstrating quantitative initiator efficiency. Overall, organic PCs inO-ATRP rival metal ATRP catalysts in polymerization performance, able topolymerize a variety of methacrylates and acrylates. First principlescalculations inspired the discovery of these PCs, provided insight intowhy 3 proved a highly efficient PC, and ultimately led to the design of6, which proved to have outstanding properties.

In another aspect of the present invention, N-Aryl phenoxazines weresynthesized and introduced as strongly reducing metal-free photoredoxcatalysts in organocatalyzed atom transfer radical polymerization forthe synthesis of well-defined polymers. Experiments confirmed quantumchemical predictions that, like the dihydrophenazine analogs, thephotoexcited states of phenoxazine photoredox catalysts are stronglyreducing and achieve superior performance when they possess chargetransfer character. Phenoxazines were compared to certaindihydrophenazines and phenothiazines as photoredox catalysts to gaininsight into the performance of these catalysts and establish principlesfor catalyst design. Maintenance of a planar conformation of thephenoxazine catalyst during the catalytic cycle encourages the synthesisof well-defined macromolecules. Using these principles, a coresubstituted phenoxazine was shown to be a visible light photoredoxcatalyst that performed superior to UV-absorbing phenoxazines, as wellas known organic photocatalysts in organocatalyzed atom transfer radicalpolymerization. Using this catalyst and irradiating with white LEDsresulted in the production of polymers with targeted molecular weightsthrough achieving quantitative initiator efficiencies, which possessdispersities ranging from 1.13 to 1.31.

In various embodiments, the organic compound is at least one selectedfrom the group consisting of:

wherein: each occurrence of R is independently selected from the groupconsisting of H, C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substitutedphenyl, —OH, —O(C₁-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl); each occurrence of R₁ isindependently selected from the group consisting of phenyl, 1-naphthyland 2-naphthyl, each of which is independently substituted with at leastone R; each occurrence of R₂ and R₃ is independently selected fromphenyl and 4-phenyl-phenyl, each of which is independently substitutedwith at least one R; each occurrence of R₃, R₄, R₅, and R₆ isindependently selected from the group consisting of phenyl,4-phenyl-phenyl, 1-naphthryl, 2-naphthryl, triphenylamine,phenanthrenyl, and pyrenyl, each of which is independently substitutedwith at least one R; or a salt or solvate thereof.

In certain embodiments, R₃ and R₅ are H. In other embodiments, R₄ and R₆are H. In yet other embodiments, R₃═R₅. In yet other embodiments, R₄═R₆.In yet other embodiments, R₃ is H and R₅ is not H. In other embodiments,R₄ is H and R₆ is not H.

In various embodiments, the quenching step is an oxidative quenchingstep. In various embodiments, the quenching step is a reductivequenching step.

In various embodiments, the organic compound is at least one selectedfrom the group consisting of:

or a salt or solvate thereof. Although the bromine salts of the radicalcations are illustrated herein, the claim encompasses other salts ofthese compounds.

In another aspect, the invention provides a method of promoting reactionof at least one reagent, wherein the reaction comprises an oxidative orreductive quenching step, wherein the method comprises irradiating theat least one reagent in the presence of an organic compound with anexcited-state reduction potential that is equal to or more negative thanabout −1.0 V vs. SCE, or a salt or radical of an organic compound withan excited-state reduction potential that is equal to or more negativethan about −1.0 V vs. SCE. In some embodiments, during the course of thereaction, the salt or radical of the organic compound may or may notform a compound with an excited-state reduction potential that is equalto or more negative than about −1.0 V vs. SCE in solution. In someembodiments, the salt or radical of the organic compound itself acts asthe catalyst.

Definitions

As used herein, each of the following terms has the meaning associatedwith it in this section.

As used herein, unless defined otherwise, all technical and scientificterms generally have the same meaning as commonly understood by one ofordinary skill in the art to which this invention belongs. Generally,the nomenclature used herein and the laboratory procedures in cellculture, molecular genetics, organic chemistry, and peptide chemistryare those well-known and commonly employed in the art.

As used herein, the articles “a” and “an” refer to one or to more thanone (i.e. to at least one) of the grammatical object of the article. Byway of example, “an element” means one element or more than one element.

As used herein, the term “about” will be understood by persons ofordinary skill in the art and will vary to some extent on the context inwhich it is used. As used herein, “about” when referring to a measurablevalue such as an amount, a temporal duration, and the like, is meant toencompass variations of ±20% or ±10%, more preferably ±5%, even morepreferably ±1%, and still more preferably ±0.1% from the specifiedvalue, as such variations are appropriate to perform the disclosedmethods.

As used herein, the term “alkyl,” by itself or as part of anothersubstituent means, unless otherwise stated, a straight or branched chainhydrocarbon having the number of carbon atoms designated (i.e., C₁-C₁₀means one to ten carbon atoms) and includes straight, branched chain, orcyclic substituent groups. Examples include methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, andcyclopropylmethyl. Most preferred is (C₁-C₆)alkyl, such as, but notlimited to, ethyl, methyl, isopropyl, isobutyl, n-pentyl, n-hexyl andcyclopropylmethyl.

As used herein, the term “electromagnetic radiation” includes radiationof one or more frequencies encompassed within the electromagneticspectrum. Non-limiting examples of electromagnetic radiation comprisegamma radiation, X-ray radiation, UV radiation, visible radiation,infrared radiation, microwave radiation, radio waves, and electron beam(e-beam) radiation. In one aspect, electromagnetic radiation comprisesultraviolet radiation (wavelength from about 10 nm to about 380 nm),visible radiation (wavelength from about 380 nm to about 700 nm) orinfrared radiation (radiation wavelength from about 700 nm to about 1mm). Ultraviolet or UV light as described herein includes UVA light,which generally has wavelengths between about 320 and about 400 nm, UVBlight, which generally has wavelengths between about 290 nm and about320 nm, and UVC light, which generally has wavelengths between about 200nm and about 290 nm. UV light may include UVA, UVB, or UVC light aloneor in combination with other type of UV light. In one embodiment, the UVlight source emits light between about 350 nm and about 400 nm. In someembodiments, the UV light source emits light between about 400 nm andabout 500 nm.

As used herein, the term “halo” or “halogen” alone or as part of anothersubstituent means, unless otherwise stated, a fluorine, chlorine,bromine, or iodine atom, preferably, fluorine, chlorine, or bromine,more preferably, fluorine or chlorine.

As used herein, the term “instructional material” includes apublication, a recording, a diagram, or any other medium of expressionthat may be used to communicate the usefulness of the compositions ofthe invention. In one embodiment, the instructional material may be partof a kit useful for generating a polymer system of the invention. Theinstructional material of the kit may, for example, be affixed to acontainer that contains the compositions of the invention or be shippedtogether with a container that contains the compositions. Alternatively,the instructional material may be shipped separately from the containerwith the intention that the recipient uses the instructional materialand the compositions cooperatively. For example, the instructionalmaterial is for use of a kit; instructions for use of the compositions;or instructions for use of a formulation of the compositions.

As used herein, the term “polymer” refers to a molecule composed ofrepeating structural units typically connected by covalent chemicalbonds. The term “polymer” is also meant to include the terms copolymerand oligomers.

As used herein, the term “polymerization” refers to at least onereaction that consumes at least one functional group in a monomericmolecule (or monomer), oligomeric molecule (or oligomer) or polymericmolecule (or polymer), to create at least one chemical linkage betweenat least two distinct molecules (e.g., intermolecular bond), at leastone chemical linkage within the same molecule (e.g., intramolecularbond), or any combination thereof. A polymerization reaction may consumebetween about 0% and about 100% of the at least one functional groupavailable in the system. In one embodiment, polymerization of at leastone functional group results in about 100% consumption of the at leastone functional group. In another embodiment, polymerization of at leastone functional group results in less than about 100% consumption of theat least one functional group.

As used herein, the term “reactive” as applied to a chemical groupregarding a reaction indicates that this group, when submitted toappropriate conditions, may take part in the reaction in question.

As used herein, the term “scaffold” refers to a two-dimensional or athree-dimensional supporting framework. A scaffold can form a two- orthree-dimensional structure of controlled mesh size. A monolayer is anon-limiting exemplary two-dimensional structure.

Throughout this disclosure, various aspects of the invention may bepresented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible sub-ranges as well asindividual numerical values within that range and, when appropriate,partial integers of the numerical values within ranges. For example,description of a range such as from 1 to 6 should be considered to havespecifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well asindividual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5,5.3, and 6. This applies regardless of the breadth of the range.

Although the description herein contains many embodiments, these shouldnot be construed as limiting the scope of the invention but as merelyproviding illustrations of some of the presently preferred embodimentsof the invention.

Every formulation or combination of components described or exemplifiedcan be used to practice the invention, unless otherwise stated. Specificnames of compounds are intended to be exemplary, as it is known that oneof ordinary skill in the art can name the same compounds differently.When a compound is described herein such that a particular isomer orenantiomer of the compound is not specified, for example, in a formulaor in a chemical name, that description is intended to include eachisomers and enantiomer of the compound described individual or in anycombination.

All references throughout this application (for example, patentdocuments including issued or granted patents or equivalents; patentapplication publications; and non-patent literature documents or othersource material) are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference, to theextent each reference is at least partially not inconsistent with thedisclosure in this application (for example, a reference that ispartially inconsistent is incorporated by reference except for thepartially inconsistent portion of the reference).

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, numerous equivalents to thespecific procedures, embodiments, claims, and examples described herein.Such equivalents were considered to be within the scope of thisinvention and covered by the claims appended hereto. For example, itshould be understood, that modifications in reaction conditions,including but not limited to reaction times, reaction size/volume, lightsource, wavelength, flux, and irradiation procedure, and experimentalreagents, such as solvents, catalysts, pressures, atmosphericconditions, e.g., nitrogen atmosphere, and reducing/oxidizing agents,with art-recognized alternatives and using no more than routineexperimentation, are within the scope of the present application. Ingeneral the terms and phrases used herein have their art-recognizedmeaning, which can be found by reference to standard texts, journalreferences and contexts known to those skilled in the art. Any precedingdefinitions are provided to clarify their specific use in the context ofthe invention.

The following examples further illustrate aspects of the presentinvention. However, they are in no way a limitation of the teachings ordisclosure of the present invention as set forth herein.

EXAMPLES

The invention is now described with reference to the following Examples.These Examples are provided for the purpose of illustration only, andthe invention is not limited to these Examples, but rather encompassesall variations that are evident as a result of the teachings providedherein.

Materials and Methods

(a) General

Phenoxazine was purchased from Beantown Chemical. 4-biphenyl boronicacid was purchased from TCI America. Glacial acetic acid was purchasedfrom VWR. All other reagents were purchased from Sigma-Aldrich. Thosechemicals used in polymerizations, including methyl methacrylate (MMA),isobutyl methacrylate (BMA), isodecyl methacrylate (IDMA), benzylmethacrylate (BnMA), n-butyl acrylate (BA), styrene (St),2,2,2-trifluoroethyl methacrylate (TFEMA), di(ethylene glycol)methacrylate (DEGMA), vinyl acetate (VA), acrylonitrile (AN), ethylα-bromophenylacetate (EBP), diethyl 2-bromo-2-methyl malonate (DBMM),dimethylformamide (DMF), trimethylsilylhydroxyethyl methacrylate(TMSHEMA), ethyl α-chlorophenylacetate (EClP), methyl α-bromoisobutyrate(MBriB), methyl bromopropionate (MBP), 2-bromopropionitrile (BrPN), anddimethylacetamide (DMA) were purified by vacuum distillation followed bythree freeze-pump-thaw cycles and stored under a nitrogen atmospherebefore use. Dioxane was purified using an mBraun MB-SPS-800 solventpurification system and kept under nitrogen atmosphere.

2-Dicyclohexylphosphino-2,6-diisopropoxybiphenyl (RuPhos) andChloro-(2-Dicyclohexylphosphino-2,6-diisopropoxy-1,1-biphenyl)[2-(2-aminoethyl)phenyl] palladium(II)-methyl-t-butyl ether adduct(RuPhos precatalyst) were stored under nitrogen atmosphere. Aryl halidesused in the catalyst synthesis were degassed and stored under nitrogen.All other reagents were used as received. The visible light source was a16-inch strip of double-density white LEDs, purchased from CreativeLighting Solutions (item no. CL-FRS1210-5M-12V-WH), wrapped inside a 400mL beaker. A VOGUE Professional Double Wide UV lamp light Nail Dryer(ND-562) was used for UV irradiation.

(b) Analytical Techniques

¹H, ¹³C, and ¹⁹F NMR spectroscopy were performed in a Varian INOVA 300MHz, 400 MHz, or 500 MHz spectrometer, as specified. Chemical shifts arereferenced to the internal solvent resonance and reported asparts-per-million relative to tetramethylsilane. Analysis of polymermolecular weights was performed via gel permeation chromatography (GPC)coupled with multi-angle light scattering (MALS), using an Agilent HPLCfitted with one guard column and two PLgel 5 μm MIXED-C gel permeationcolumns, a Wyatt Technology TrEX differential refractometer, and a WyattTechnology miniDAWN TREOS light scattering detector, using THF as theeluent at a flow rate of 1.0 mL/min. Ultraviolet-visible spectroscopywas performed on an Agilent spectrophotometer using DMF as the solvent.Emission spectroscopy was performed on a SLM 8000C spectrofluorimeterusing DMF as the solvent. Samples were sparged with argon for 15 minutesprior to analysis. Cyclic voltammetry was performed with a CHInstruments electrochemical analyzer with a Ag/AgNO₃ (0.01 M in MeCN)reference electrode using MeCN as the solvent. Samples were sparged withargon for 5 minutes prior to analysis. ESI mass spectrometry analysiswas performed on a Waters Synapt G2 HDMS Qtof using acetonitrile as thesolvent. MALDI-TOF mass spectrometry analysis was performed on a BrukerMicroflex-LRF mass spectrometer in positive ion, reflector mode usingTHF as the solvent

(c) General Polymerization Procedure

A 20 mL vial was charged with a small stirbar and catalyst andtransferred into a nitrogen-atmosphere glovebox. Solvent, monomer, andinitiator were then added sequentially via pipette. The vial was thensealed, placed inside a beaker illuminated by white LED light, andstirred (FIG. 5). To analyze the progress of a polymerization at a giventime point (e.g. for kinetic analysis or for the “on/off” irradiationexperiment), a 0.2 mL aliquot of the reaction media was removed viasyringe and injected into a vial containing 0.7 mL CDCl₃ with 250 ppmbutylated hydroxytoluene (BHT). This aliquot was then analyzed by ¹HNMR, subsequently allowed to dry, and then re-dissolved in THF forfurther analysis by SEC-MALS. After a polymerization was consideredapproximately complete (according to the time specified in the variousdata tables), the reaction was removed from the glovebox, poured into a20-fold excess of methanol with respect to the total reaction volume,stirred, and the product polymer was then isolated by vacuum filtrationand washed with excess methanol.

For copolymers specified as isolated, isolation was performed by pouringthe reaction mixture into a 50-fold excess of CH₃OH, causing the polymerto precipitate. After 1 hour of stirring, the precipitate was collectedvia vacuum filtration and dried under reduced pressure. NMR analysis ofpoly(DEGMA) and poly(TFEMA) was performed by pouring their respectivereaction mixtures into 50 mL water, stirring for 1 hour, and collectingthe precipitate via vacuum filtration. NMR analysis of poly(TMSHEMA) wasperformed by pouring the reaction mixture into 50 mL CH₂Cl₂, stirringfor 1 hour, and collecting the precipitate via vacuum filtration.

Control polymerizations revealed no polymerization occurred in theabsence of any single component (i.e. light, PC, or initiator), or inthe presence of oxygen or TEMPO, (supporting a radical polymerizationmechanism).

(d) Procedure for Polymerizations Performed in Natural Sunlight

A 20 mL vial was charged with a small stirbar and catalyst (9.35 μmol,1.00 eq.) and transferred into a nitrogen-atmosphere glovebox. DMA (1.00mL), MMA (1.00 mL, 9.35 mmol, 1000 eq.) and EBP (16.4 μL, 93.5 μmol,10.0 eq.) were added sequentially via pipette. The vials were thenremoved from the glovebox, sealed with electrical tape, and placed inthe sunlight from 9 AM to 4 PM (FIG. 6).

(e) Synthesis

5,10-dihydrophenazine

A 500 mL round bottom flask was charged with a mixture of H₂O (200 mL),EtOH (50 mL), and a stir bar. The mixture was sparged with nitrogen for30 minutes and then phenazine (2.00 g, 27.8 mmol, 1.00 eq.) and Na₂S₂O₄(23.3 g, 278 mmol, 10.0 eq.) were then added. This mixture wassubsequently heated at reflux under nitrogen atmosphere for 3 h. Aftercooling to RT, the product was isolated as a precipitate via cannulafiltration, washed with excess deoxygenated H₂O, and dried under reducedpressure to yield a light green powder (1.35 g, 7.42 mmol, 67%). Theproduct was stored under nitrogen until further use.

5,10-di(4-methoxyphenyl)-5,10-dihydrophenazine (1)

An oven-dried vacuum tube was charged with 5,10-dihydrophenazine (1.00g, 5.50 mmol, 1.00 eq.), NaO^(t)Bu (2.11 g, 22.00 mmol, 4.00 eq.),RuPhos (103 mg, 0.22 mmol, 0.04 eq.), RuPhos precatalyst (180 mg, 0.22mmol, 0.04 eq.), 4-bromoanisole (4.05 g, 22.0 mmol, 4.00 eq), and 8.00mL dioxane. This flask was sealed under nitrogen and heated at 110° C.for 10 h. After cooling to room temperature, 200 mL CH₂Cl₂ was added tothe reaction mixture and this was extracted three times with 200 mL H₂O.The organic layer was dried with MgSO₄, filtered, and the volatiles wereremoved under reduced pressure to reveal a brown solid. Purification bycolumn chromatography (1:3 mixture of CH₂Cl₂ and hexanes) afforded theproduct 1 as a light yellow solid (1.00 g, 2.53 mmol, 46%). ¹H NMR(C₆D₆, 500 MHz): δ 7.11-7.02 (m, 4H), 6.78-6.67 (m, 4H), 6.33 (dd,J=5.9, 3.4 Hz, 4H), 5.89 (dd, J=5.8, 3.5 Hz, 4H), 3.23 (s, 6H). ¹³C NMR(C₆D₆, 100 MHz): δ 54.53, 112.60, 116.33, 120.94, 127.52, 132.18,137.24, 159.05. HRMS (ESI): calc'd for M+ C₂₆H₂₂N₂O₂, 394.1681; found394.1675. UV/Vis: λ_(max) 372 nm.

5,10-diphenyl-5,10-dihydrophenazine (2)

An oven-dried vacuum tube was charged with 5,10-dihydrophenazine (1.00g, 5.50 mmol, 1.00 eq.), NaO^(t)Bu (2.11 g, 22.00 mmol, 4.00 eq.),RuPhos (103 mg, 0.22 mmol, 0.04 eq.), RuPhos precatalyst (180 mg, 0.22mmol, 0.04 eq.), iodobenzene (4.49 g, 22.0 mmol, 4.00 eq), and 8.00 mLdioxane. This flask was sealed under nitrogen and heated at 110° C. for10 h. After cooling to room temperature, 200 mL CH₂Cl₂ was added to thereaction mixture and this was extracted three times with 200 mL H₂O. Theorganic layer was dried with MgSO₄, filtered, and the volatiles wereremoved under reduced pressure to reveal a red-brown solid. Purificationby column chromatography (1:3 mixture of CH₂Cl₂ and hexanes) affordedthe product 2 as a light yellow solid (1.27 g, 3.80 mmol, 69%). Furtherpurification by layering a solution of the product in CH₂Cl₂ withhexanes gave 2 as yellow needles. ¹H NMR (C₆D₆, 400 MHz): δ 7.16 (couldnot be resolved from NMR solvent peak), 7.07-7.00 (m, 2H), 6.31-6.25 (m,4H), 5.85-5.79 (m, 4H). ¹³C NMR (C₆D₆, 100 MHz): δ 112.69, 121.03,127.69, 131.03, 131.22, 136.75, 140.38. HRMS (ESI): calc'd for M+C₂₄H₁₈N₂, 334.1470; found 334.1482. UV/Vis: λ_(max) 369 nm.

5,10-di(4-trifluoromethylphenyl)-5,10-dihydrophenazine (3)

An oven-dried vacuum tube was charged with 5,10-dihydrophenazine (1.01mg, 5.55 mmol, 1.00 eq.), NaO^(t)Bu (2.13 g, 22.22 mmol, 4.00 eq.),RuPhos (102 mg, 0.22 mmol, 0.04 eq.), RuPhos precatalyst (180 mg, 0.22mmol, 0.04 eq.), 4-bromobenzotrifluoride (5.00 g, 22.22 mmol, 4.00 eq),and 8.00 mL dioxane. This flask was sealed under nitrogen and heated at110° C. for 10 h. After cooling to room temperature, 200 mL CH₂Cl₂ and200 mL H₂O was added to the reaction flask, causing the product toprecipitate. Filtration and washing with CH₂Cl₂ afforded 3 as a lightyellow powder (1.65 g, 3.52 mmol, 63%). Further purification by layeringa solution of the product in CH₂Cl₂ with hexanes gave 3 as light yellowneedles. ¹H NMR (C₆D₆, 400 MHz) δ 7.25 (d, J=8.1 Hz, 4H), 6.90 (d, J=8.0Hz, 4H), 6.36-6.30 (m, 4H), 5.69-5.63 (m, 4H). ¹³C NMR (C₆D₆, 100 MHz):δ 113.26, 121.65, 128.17, 127.52, 128.21, 131.32, 135.91, 143.54. ¹⁹FNMR (C₆D₆, 376 MHz): δ −62.23. HRMS (ESI): calc'd for M+ C₂₆H₁₆F₆N₂,470.1218; found 470.1216. UV/Vis: λ_(max) 367 nm.

5,10-di(4-cyanophenyl)-5,10-dihydrophenazine (4)

An oven-dried vacuum tube was charged with 5,10-dihydrophenazine (500mg, 2.75 mmol, 1.00 eq.), NaO^(t)Bu (1.06 g, 11.00 mmol, 4.00 eq.),RuPhos (51 mg, 0.11 mmol, 0.04 eq.), RuPhos precatalyst (90 mg, 0.11mmol, 0.04 eq.), 4-bromobenzonitrile (2.00 g, 11.0 mmol, 4.00 eq), and3.00 mL dioxane. This flask was sealed under nitrogen and heated at 110°C. for 10 h. After cooling to room temperature, 200 mL CH₂Cl₂ was addedto the reaction mixture and this was extracted three times with 200 mLH₂O. The organic layer was dried with MgSO₄, filtered, and the volatileswere removed under reduced pressure to reveal a brown solid.Purification by column chromatography (1:1 mixture of CH₂Cl₂ andhexanes) produced the product 4 as a brown powder (718 mg, 1.87 mmol,68%). Further purification by layering a solution of the product inCH₂Cl₂ with hexanes gave 4 as dark gold needles. ¹H NMR (C₆D₆, 400 MHz)δ 6.98-6.89 (m, 4H), 6.73-6.64 (m, 4H), 6.42-6.36 (m, 4H), 5.72-5.66 (m,4H). ¹³C NMR (C₆D₆, 100 MHz): δ 111.56, 114.16, 117.82, 121.96, 130.35,134.52, 135.69, 144.12. HRMS (ESI): calc'd for M+ C₂₆H₁₆N₄, 384.1375;found 384.1370. UV/Vis: λ_(max) 321 nm.

5,10-di(2-naphthyl)-5,10-dihydrophenazine (5)

An oven-dried vacuum tube was charged with 5,10-dihydrophenazine (911mg, 5.00 mmol, 1.00 eq.), NaOtBu (1.92 g, 20.0 mmol, 4.00 eq.), RuPhos(46.7 mg, 0.10 mmol, 0.04 eq.), RuPhos precatalyst (81.7 mg, 0.10 mmol,0.04 eq.), 2-bromonaphthalene (4.14 g, 20.0 mmol, 4.00 eq), and 10.0 mLdioxane. This flask was sealed under nitrogen and heated at 110° C. for10 h. After cooling to room temperature, 250 mL CH₂Cl₂ and 250 mL H₂Owere added to the reaction flask, causing the product to precipitate.Filtration and washing with CH₂Cl₂ afforded 6 as a light yellow-greenpowder (1.95 g, 4.50 mmol, 90%). ¹H NMR (C₆D₆, 300 MHz) δ 7.67 (dd, 4H),7.63-7.47 (m, 4H), 7.36-7.16 (m, 8H), 6.33-6.21 (dd, 4H), 5.91-5.79 (dd,4H). ¹³C NMR (C₆D₆, 75 MHz): δ 137.77, 136.91, 135.29, 132.99, 131.63,130.54, 128.80, 127.83, 127.61, 126.53, 126.16, 121.30, 113.09. HRMS(ESI): calc'd for M+ C₃₂H₂₂N₂ 434.1783; found 434.1777. UV/Vis: λmax 340nm.

5,10-di(1-naphthyl)-5,10-dihydrophenazine (6)

6 was synthesized using a modified literature procedure (20). Anoven-dried vacuum tube was charged with 5,10-dihydrophenazine (911 mg,5.00 mmol, 1.00 eq.), NaO^(t)Bu (1.92 g, 20.0 mmol, 4.00 eq.), RuPhos(46.7 mg, 0.10 mmol, 0.04 eq.), RuPhos precatalyst (81.7 mg, 0.10 mmol,0.04 eq.), 1-bromonaphthalene (4.14 g, 20.0 mmol, 4.00 eq), and 10.0 mLdioxane. This flask was sealed under nitrogen and heated at 110° C. for48 h. After cooling to room temperature, 250 mL CH₂Cl₂ and 250 mL H₂Owas added to the reaction flask, causing the product to precipitate.Filtration and washing with CH₂Cl₂ afforded 6 as a yellow powder (0.06g, 0.15 mmol, 3%). ¹H NMR (C₆D₆, 400 MHz) δ 8.64-8.54 (m, 2H), 7.73-7.63(m, 4H), 7.47 (m, 2H), 7.33-7.22 (m, 6H), 6.12-6.03 (dd, 4H), 5.70-5.63(dd, 4H). ¹³C NMR (C₆D₆, 100 MHz): δ 136.65, 135.98, 129.27, 128.61,128.41, 127.69, 127.46, 127.04, 126.94, 126.51, 123.89, 121.23, 112.97.HRMS (ESI): calc'd for M+ C₃₂H₂₂N₂, 434.1783; found 434.1771. UV/Vis:λ_(max) 362 nm.

Synthesis of N-aryl phenoxazine catalyst (Example 7)10-Phenylphenoxazine

A 50 mL storage flask was charged with a stir bar, flame dried undervacuum and back filled with nitrogen three times. The flask was thencharged with phenoxazine (183 mg, 1.0 mmol, 1.00 eq.), NaO^(t)Bu (192.2mg, 2.0 mmol, 2.00 eq.), and RuPhos (12 mg, 0.03 mmol, 0.03 eq.). Theflask was taken into a nitrogen filled glovebox where RuPhos Precat (21mg, 0.03 mmol, 0.03 eq.), 1 mL dry dioxane and bromobenzene (0.11 mL,2.0 mmol 2.00 eq.) were added. The flask was placed in an oil bath at130° C. while stirring for 48 hours. The flask was then cooled to roomtemperature, diluted with CH₂Cl₂, and the solution was washed with waterthree times, brine once, dried over MgSO₄ and purified byrecrystallization from CH₂Cl₂ layered with hexanes at −25° C. to give 60mg of yellow crystals, 23% yield.

4-Trifluoromethylphenyl-10-phenoxazine, or10-(4-(trifluoromethyl)phenyl)-10H-phenoxazine

A 100 mL storage flask was charged with a stir bar, flame dried undervacuum and back filled with nitrogen three times. The flask was thencharged with phenoxazine (800 mg, 4.37 mmol, 1.00 eq.), NaOtBu (840 mg,8.74 mmol, 2.00 eq.), and RuPhos (52.4 mg, 0.13 mmol, 0.03 eq.). Theflask was placed into a nitrogen filled glovebox where RuPhos Precat(91.77 mg, 0.13 mmol, 0.03 eq.), and 4 mL dry dioxane and4-bromobenzotrifluoride (1.22 mL, 8.74 mmol, 2.00 eq.) were added. Theflask was placed in an oil bath at 130° C. while stirring for 48 hours.The flask was then cooled to room temperature, diluted with CH₂Cl₂, andthe solution was washed with water three times, brine once, dried overMgSO₄ and purified by recrystallization from CH₂Cl₂ layered with hexaneson top at −25° C. to yield 987 mg of yellow crystals, 69% yield. Finalpurification was conducted via sublimation at 100 mTorr at 175° C. ¹HNMR (CDCl₃, 500 MHz) δ 7.87 (d, J=8.20 Hz, 2H), 7.51 (d, J=8.15 Hz, 2H),6.73 (dd, J=7.85, 1.75 Hz, 2H), 6.68 (m, 2H), 6.62 (td, J=7.85, 1.75 Hz,2H), 5.90 (d, J=8.20 Hz, 2H). 13C NMR (CDCl₃, 400 MHz) δ 144.10, 142.73,133.89, 131.76, 130.97, 130.64, 128.44, 123.52, 122.09, 115.93, 113.39.19F NMR (CDCl3, 300 MHz) δ 62.55. HRMS (ESI): calculated for M⁺C₁₉H₁₂F₃NO, 327.0871; observed 327.0869.

1-Naphthalene-10-phenoxazine, or 10-(naphthalen-1-yl)-10H-phenoxazine

A stir bar was placed into a 100 mL storage flask, flame dried undervacuum and then back filled with nitrogen three times. The flask wasthen charged with phenoxazine (1.00 g, 5.46 mmol, 1.00 eq.), NaO^(t)Bu(1.054 g, 10.92 mmol, 2.00 eq.), and RuPhos (65.6 mg, 0.16 mmol, 0.03eq.). The flask was taken into a nitrogen filled glovebox where RuPhosPrecat (114.75 mg, 0.16 mmol, 0.03 eq.), 6 mL dry dioxane and1-bromonaphthalene (1.53 mL, 10.92 mmol, 2.00 eq.) were added. The flaskwas placed in an oil bath at 130° C. while stirring for 48 hours. Theflask was then cooled to room temperature, diluted with CH₂Cl₂, and thesolution was washed with water three times, brine once, dried over MgSO₄and purified by recrystallization from CH₂Cl₂ layered with hexanes ontop at −25° C. to yield 790 mg of yellow crystals, 47% yield. Finalpurification was conducted via sublimation at 100 mTorr at 190° C. ¹HNMR (CDCl₃, 500 MHz) δ 8.08 (d, J=8.35 Hz, 1H), 7.99 (dd, J=8.20, 3.95Hz, 2H), 7.66 (t, J=7.25 Hz, 1H), 7.56 (m, 2H), 7.48 (m, 1H), 6.74 (dd,J=7.90, 1.45 Hz, 2H), 6.63 (t, J=7.85 Hz, 2H), 6.49 (td, J=7.85, 1.45Hz, 2H), 5.71 (dd, J=7.90, 1.45 Hz, 2H). ¹³C NMR (CDCl₃, 400 MHz) δ144.09, 135.77, 135.24, 134.48, 131.56, 129.35, 129.14, 128.95, 127.50,127.07, 127.04, 123.57, 123.53, 121.47, 115.58, 113.57. HRMS (ESI):calculated for M+ C₂₂H₁₅NO, 309.1154; observed 309.1152.

2-Naphthalene-10-phenoxazine, or 10-(naphthalen-2-yl)-10H-phenoxazine

A 100 mL storage flask was charged with a stir bar, flame dried undervacuum then back filled with nitrogen three times. The flask was thencharged with phenoxazine (1.00 g, 5.46 mmol, 1.00 eq.), NaO^(t)Bu (1.054g, 10.92 mmol, 2.00 eq.), and RuPhos (65.6 mg, 0.16 mmol, 0.03 eq.). Theflask was taken into a nitrogen filled glovebox where RuPhos Precat(114.75 mg, 0.16 mmol, 0.03 eq.), 6 mL dry dioxane and2-bromonaphthalene (2.26 mg, 10.92 mmol, 2.00 eq.) were added. The flaskwas placed in an oil bath at 130° C. while stirring for 48 hours. Theflask was then cooled to room temperature, diluted with CH₂Cl₂, and thesolution was washed with water three times, brine, dried over MgSO4 andpurified by recrystallization from CH₂Cl₂ at −25° C. to yield 890 mg oflight yellow, flakey crystals, 53% yield. Final purification wasconducted via sublimation at 100 mTorr at 195° C. ¹H NMR (CDCl₃, 400MHz) δ 8.08 (d, J=8.60 Hz, 1H), 7.95 (d, J=7.00 Hz, 1H), 7.88 (m, 2H),7.57 (m, 2H), 7.42 (dd, J=8.64, 2.04 Hz, 1H), 6.73 (dd, J=7.84, 1.56 Hz,2H), 6.66 (t, J=7.52, 2H), 6.57 (td, J=8.12, 1.60 Hz, 2H), 5.99 (d,J=7.96, 2H). ¹³C NMR (CDCl₃, 400 MHz) δ 144.42, 136.74, 135.06, 134.78,133.28, 131.55, 130.29, 128.23, 128.15, 127.12, 126.78, 123.49, 121.66,115.74, 113.78. HRMS (ESI): calculated for M+ C₂₂H₁₅NO, 309.1154;observed 309.1151.

1-Naphthalene-10-phenothiazine (or10-(naphthalen-1-yl)-10H-phenothiazine)

A stir bar was placed in a 50 mL storage flask, flame dried under vacuumand then back filled with nitrogen three times. The flask was thencharged with phenothiazine (0.600 g, 3.01 mmol, 1.00 eq.), NaO^(t)Bu(0.578 g, 6.02 mmol, 2.00 eq.), and RuPhos (42.2 mg, 0.09 mmol, 0.03eq.). The flask was taken into a nitrogen filled glovebox where RuPhosPrecat (73.8 mg, 0.09 mmol, 0.03 eq.), 3 mL dry Dioxane and1-bromonaphthalene (0.84 mg, 6.02 mmol, 2.00 eq.) were added. The flaskwas placed in an oil bath at 130° C. while stirring for 48 hours. Theflask was then cooled to room temperature, diluted with CH₂Cl₂, and thesolution was washed with water three times, brine once, dried over MgSO₄and purified by recrystallization from CH₂Cl₂ layered with hexanes ontop at −25° C. to yield 253 mg of a yellowish solid, 26% yield. Finalpurification was conducted via sublimation at 100 mTorr at 155° C.

3,7-Dibromo 1-Naphthalene-10-phenoxazine (or3,7-dibromo-10-(naphthalen-1-yl)-10H-phenoxazine)

1-Naphthalane-10-phenoxazine (800 mg, 2.58 mmol, 1 eq.) was dissolved in80 mL of chloroform. 80 mL of glacial acetic acid was then added to thestirring mixture. Aluminum foil was thoroughly wrapped around to coverthe reaction vial, blocking out light. In the dark, powderedN-Bromosuccinimide (944 mg, 5.30 mmol, 2.05 eq.) was added in smallportions over a 20 minute period. After 2 hours at room temperature thereaction mixture was concentrated under vacuum. The resulting solid waswashed three times with water, brine, then dried with MgSO₄. A light tanpowder (1.0 g, 2.14 mmol, 82.8% yield) was collected. This was used forthe Suzuki coupling without further purification. ¹H NMR (C₆D₆, 500 MHz)δ 7.82 (d, J=8.48 Hz, 1H), 7.57 (dd, J=25.02, 8.3 Hz, 2H), 7.19 (m, 1H),7.12 (t, J=8.03 Hz, 2H), 6.88 (dd, J=7.32, 0.57 Hz, 3H), 6.84 (d, J=2.19Hz, 2H), 6.36 (dd, J=8.54, 2.21 Hz, 2H). ¹³C NMR (CDCl₃, 400 MHz)δ144.27, 135.82, 134.22, 133.32, 130.91, 129.88, 129.15, 128.87, 127.83,127.29, 127.06, 126.62, 123.02, 118.86, 114.74, 113.06.

3,7-Di(4-biphenyl) 1-Naphthalene-10-Phenoxazine, or3,7-di([1,1′-biphenyl]-4-yl)-10-(naphthalen-1-yl)-10H-phenoxazine

A 200 mL schlenk flask was flame dried, filled with nitrogen, andequipped with a stir bar and reflux condenser before 3,7-Dibromo1-Naphthalene-10-phenoxazine (225 mg, 0.48 mmol, 1 eq.),4-biphenylboronic acid (381.8 mg, 1.9 mmol, 4 eq.) was added, thendissolved in 20 mL of THF. 6 mL of K₂CO₃ (2M) was syringed into thesolution and then heated to 80° C. and stirred for 20 minutes. Afterwhich, Palladium tetrakis(triphenylphosphine) (93 mg, 15% mol) in a 20mL solution of THF was added then heated to 100° C. and left to run for24 hours. Once complete, the reaction was concentrated under vacuum,dissolved in DCM, and washed with water two times, brine, then driedwith MgSO₄. A bright yellow powder was collected (270 mg, 0.44 mmol,91.6% yield) after recrystallization in DCM/Methanol. ¹H NMR (C₆D₆, 500MHz) δ 8.18 (d, J=8.35 Hz, 1H), 7.69 (d, J=8.09 Hz, 2H), 7.66 (dd,J=7.21, 2.22 Hz, 2H), 7.51 (d, J=7.21 Hz, 4H), 7.46 (m, 8H), 7.37 (d,J=2.0 Hz, 2H), 7.25 (m, 8H), 6.73 (dd, J=2.03 Hz, 2H), 5.88 (d, J=8.28Hz, 2H). ¹³C NMR (C₆D₆, 300 MHz) δ 144.49, 140.93, 139.74, 139.02,135.69, 135.17, 134.49, 133.60, 131.47, 129.06, 128.82, 128.72, 127.52,127.08, 126.95, 126.86, 126.76, 126.56, 123.38, 122.05, 114.23, 113.98.

Synthesis of 3-Phenyl Phenyl-10-Phenoxazine

3-bromo phenyl-10-phenoxazine (0.170 g, 0.502 mmol, 1.00 equiv.) andphenyl boronic acid (0.122 g, 1.00 mmol, 2.00 equiv.) were added to astorage tube and cycled between vacuum and nitrogen three times before4.00 mL of dried and degassed THF was added. Once all reagents weredissolved, 4.00 mL of a 2.00 M aqueous solution of K2CO3, which had beensparged with nitrogen, was added. In a separate Schlenk flask,palladiumtetrakis(triphenyl phosphine) (0.0464 g, 0.0402 mmol, 0.0800equiv.) was dissolved in 4.00 mL of THF under inert atmosphere. Thesolution of Pd(PPh₃)₄ was then added to the reaction mixture and thereaction was heated at 100° C. for 48 h, before it was exposed to oxygenand allowed to cool to room temperature. The reaction mixture wasconcentrated under reduced pressure, diluted with DCM/hexanes, andpassed through a short plug of silica. The solution was then moved to aseparatory funnel, washed with de-ionized water once and brine twice.The solution was dried over magnesium sulfate, concentrated undervacuum, and recrystallized using DCM/methanol at −25° C. The product wascollected via vacuum filtration as a white solid (0.127 g, 0.378 mmol,75.2% yield). 1H NMR (C6D6, 400 MHz) δ 7.40-7.30 (m, 2H), 7.15-7.06 (m,1H), 7.10-6.93 (m, 6H), 6.97-6.82 (m, 2H), 6.74 (ddd, J=13.5, 8.1, 1.8Hz, 2H), 6.43 (dtd, J=31.9, 7.6, 1.5 Hz, 2H), 5.96-5.85 (m, 2H). 13C NMR(CDCl3, 75 MHz) δ 144.53, 144.17, 140.19, 139.11, 134.72, 134.35,133.84, 130.76, 130.64, 128.67, 128.05, 126.64, 126.17, 123.33, 121.69,121.54, 115.63, 114.24, 113.63, 113.46. HRMS (ESI): calculated for M+C24H17NO 335.1310; observed 335.1312.

Synthesis of 3-(4-biphenyl) Phenyl-10-Phenoxazine

3-bromo phenyl-10-phenoxazine (0.450 g, 0.133 mmol, 1.00 equiv.) andbiphenyl boronic acid (0.395 g, 1.99 mmol, 1.50 equiv.) were added to astorage tube and cycled between vacuum and nitrogen three times before30 mL of dried and degassed THF was added. Once all reagents weredissolved, 11.0 mL of a 2.00 M aqueous solution of K2CO3, which had beensparged with nitrogen, was added. In a separate Schlenk flask,palladiumtetrakis(triphenyl phosphine) (0.154 g, 0.133 mmol, 0.100equiv.) was dissolved in 30.0 mL of THF under inert atmosphere. Thesolution of Pd(PPh₃)₄ was then added to the reaction mixture and thereaction was heated at 100° C. for 24 hours, before it was exposed tooxygen and allowed to cool to room temperature. The reaction mixture wasconcentrated under reduced pressure, diluted with DCM/hexanes, andpassed through a short plug of silica. The solution was then moved to aseparatory funnel, washed with de-ionized water once and brine twice.The solution was dried over magnesium sulfate, concentrated undervacuum, and recrystallized using DCM/methanol at −25° C. The product wascollected via vacuum filtration as a light yellow solid (0.506 g, 1.23mmol, 92.5% yield). 1H NMR (C6D6, 500 MHz) δ 7.54-7.49 (m, 2H), 7.46 (d,J=3.2 Hz, 4H), 7.25 (t, J=7.7 Hz, 2H), 7.21 (d, J=2.1 Hz, 1H), 7.13 (d,J=7.9 Hz, 2H), 7.08-7.02 (m, 1H), 7.00-6.96 (m, 2H), 6.84 (dt, J=8.2,1.7 Hz, 2H), 6.51 (dtd, J=40.8, 7.6, 1.5 Hz, 2H), 6.01 (d, J=8.3 Hz,1H), 5.97 (dd, J=7.9, 1.5 Hz, 1H). 13C NMR (C6D6, 75 MHz) δ 144.59,144.19, 140.97, 139.68, 139.10, 139.02, 134.32, 134.18, 133.94, 130.79,130.64, 128.71, 128.09, 127.48, 127.05, 126.95, 126.50, 123.37, 121.63,121.60, 115.65, 114.10, 113.68, 113.50. HRMS (ESI): calculated for M+C30H21NO 411.1623; observed 411.1627.

Synthesis of 3,7-Di(4-(diphenylamino)phenyl)2-Naphthalene-10-Phenoxazine

3,7-Dibromo 2-Naphthalene-10-phenoxazine (0.350 g, 0.749 mmol, 1.00equiv.) and 4-(diphenylamino) phenyl boronic acid (0.867 g, 3.00 mmol,4.00 equiv.) were added to a 250 mL storage tube flask and cycledbetween vacuum and nitrogen three times. 30.0 mL of dried and degassedTHF was added. Once all reagents were dissolved, 10.0 mL of a 2.00 Maqueous solution of K2CO₃, which had been sparged with nitrogen, wasadded and the biphasic system and was heated to 80° C. In a separateSchlenk flask, palladiumtetrakis(triphenyl phosphine) (0.130 g, 0.112mmol, 0.150 equiv.) was dissolved in 30.0 mL of THF under inertatmosphere. The solution of Pd(PPh₃)₄ was then added to the reactionmixture and the temperature was raised to 100° C. for 24 h before it wasallowed to cool to room temperature and exposed to oxygen. The reactionmixture was concentrated under reduced pressure, diluted withDCM/hexanes, and passed through a short plug of silica gel. The solutionwas then moved to a separatory funnel, washed with de-ionized waterthree times and brine one time. The solution was dried over magnesiumsulfate, concentrated under vacuum, and recrystallized usingDCM/methanol at −25° C. The product was collected as a yellow solid(0.453 mg, 0.569 mmol, 76.3% yield). ₁H NMR (C6D6, 500 MHz) δ 7.60 (m,2H), 7.53 (d, J=7.90 Hz, 1H), 7.26 (m, 11H), 7.05 (m, 24H), 6.81 (m,6H), 5.97 (d, J=8.31 Hz, 2H). ₁₃C NMR (C6D6, 300 MHz) δ 147.97, 146.92,144.51, 136.21, 134.81, 134.51, 134.42, 133.30, 133.00, 131.23, 129.91,129.25, 127.77, 127.00, 126.73, 126.35, 124.50, 124.30, 122.70, 121.36,113.93, 113.88. HRMS (ESI): calculated for M+ C₅₈H₄₁N₃O, 795.3250;observed 795.3256.

Synthesis of 3,7-Di(9-phenanthracenyl) 2-Naphthalene-10-Phenoxazine

3,7-Dibromo 2-Naphthalene-10-phenoxazine (0.350 g, 0.749 mmol, 1.00equiv.) and 9-phenanthracenyl boronic acid (0.569 g, 3.00 mmol, 4.00equiv.) were added to a 250 mL storage tube flask and cycled betweenvacuum and nitrogen three times before 30.0 mL of dried and degassed THFwas added. Once all of the reagents were dissolved, 10.0 mL of a 2.00 Maqueous solution of K₂CO₃, which had been sparged with nitrogen, wasadded and the biphasic system was heated to 80° C. In a separate Schlenkflask, palladiumtetrakis(triphenyl phosphine) (0.130 g, 0.112 mmol,0.150 equiv.) was dissolved in 30.0 mL of THF under inert atmosphere.The solution of Pd(PPh₃)₄ was then added to the reaction mixture and thereaction was heated at 100° C. for 24 h before it was allowed to cool toroom temperature and exposed to oxygen. The reaction mixture wasconcentrated under reduced pressure, diluted with DCM, and passedthrough a short plug of silica gel. The solution was then moved to aseparatory funnel, washed with de-ionized water three times and brineone time. The solution was dried over magnesium sulfate, concentratedunder vacuum, and recrystallized using DCM/methanol at −25° C. Theproduct was collected via vacuum filtration as a yellow solid (0.408 g,0.616 mmol, 82.2% yield). 1H NMR (C6D6, 500 MHz) δ 8.55 (d, J=8.13 Hz,2H), 8.49 (d, J=8.03 Hz, 2H), 8.26 (d, J=8.18 Hz, 2H), 7.64 (m, 8H),7.41 (m, 8H), 7.28 (m, 3H), 7.15 (d, J=1.82 Hz, 2H), 6.79 (dd, J=8.18,1.86 Hz, 2H), 6.14 (d, J=8.19 Hz, 2H). 13C NMR (C6D6, 300 MHz) δ 144.15,137.99, 136.31, 134.93, 134.59, 133.84, 133.09, 131.88, 131.46, 131.40,130.98, 130.16, 130.00, 128.67, 127.82, 127.77, 127.27, 126.88, 126.80,126.62, 126.44, 126.36, 126.34, 126.33, 125.25, 123.02, 122.54, 117.70,113.52. HRMS (ESI): calculated for M+ C50H31NO, 661.2405; observed661.2413.

Synthesis of 3,7-Di(1-pyrenyl) 2-Naphthalene-10-Phenoxazine

3,7-Dibromo 2-Naphthalene-10-phenoxazine (0.350 g, 0.749 mmol, 1.00equiv.) and 1-pyrene boronic acid (0.738 g, 3.00 mmol, 4.00 equiv.) wereadded to a 250 mL storage tube flask and cycled between vacuum andnitrogen three times before 30 mL of dried and degassed THF was added.Once all reagents were dissolved, 10.0 mL of a 2.00 M aqueous solutionof K₂CO₃, which had been sparged with nitrogen, was added and thebiphasic system was heated to 80° C. In a separate schlenk flask,palladiumtetrakis(triphenyl phosphine) (0.130 g, 0.112 mmol, 0.150equiv.) was dissolved in 30.0 mL of THF under inert atmosphere. Thesolution of Pd(PPh₃)₄ was then added to the reaction mixture and thereaction was heated to 100° C. for 24 h before it was allowed to cool toroom temperature and exposed to oxygen. The reaction mixture wasconcentrated under reduced pressure, diluted with DCM/Hexanes, andpassed through a short plug of silica gel. The solution was then movedto a separatory funnel, washed with de-ionized water three times andbrine one time. The solution was dried over magnesium sulfate,concentrated under vacuum, and recrystallized using DCM/methanol at −25°C. The product was collected via vacuum filtration as a yellow solid(0.376 g, 0.530 mmol, 70.8% yield). ₁H NMR (C6D6, 500 MHz) δ 7.86 (d,J=8.34 Hz, 1H), 7.37 (m, 2H), 7.24 (m, 5H), 7.06 (d, J=2.05 Hz, 2H),6.90 (m, 17H), 6.43 (dd, J=8.30, 2.11 Hz, 2H), 5.57 (d, J=8.32 Hz, 2H).₁₃C NMR (C6D6, 300 MHz) δ 144.30, 136.93, 136.24, 135.05, 134.95,133.79, 133.12, 131.65, 131.48, 131.23, 130.64, 13.02, 128.85, 128.73,127.83, 127.79, 127.47, 127.26, 126.85, 126.47, 125.98, 125.85, 125.43,125.29, 125.28, 125.11, 125.01, 124.84, 124.80, 124.58, 118.09, 113.65.HRMS (ESI): calculated for M+ C₅₄H₃₅NO, 709.2405; observed 709.2407.

Synthesis of 3,7-Di(2-naphthyl) 2-Naphthalene-10-Phenoxazine

3,7-Dibromo 2-Naphthalene-10-phenoxazine (0.400 g, 0.856 mmol, 1.00equiv.) and 2-naphthalene boronic acid (0.589 g, 3.43 mmol, 4.00 equiv.)were added to a 250 mL storage tube flask and cycled between vacuum andnitrogen three times before 37.0 mL of dried and degassed THF was added.Once all reagents were dissolved, 11.0 mL of a 2.00 M aqueous solutionof K₂CO₃, which had been sparged with nitrogen, was added and thebiphasic system was heated to 80° C. In a separate Schlenk flask,palladiumtetrakis(triphenyl phosphine) (0.148 g, 0.128 mmol, 0.150equiv.) was dissolved in 37.0 mL of THF under inert atmosphere. Thesolution of Pd(PPh₃)₄ was then added to the reaction mixture and thereaction was heated at 100° C. for 24 h before it was allowed to cool toroom temperature and exposed to oxygen. The reaction mixture wasconcentrated under reduced pressure, diluted with DCM/Hexanes, andpassed through a short plug of silica gel. The solution was then movedto a separatory funnel, washed with de-ionized water three times andbrine one time. The solution was dried over magnesium sulfate,concentrated under vacuum, and recrystallized using DCM/methanol at −25°C. The product was collected via vacuum filtration as a yellow solid(0.481 g, 0.281 mmol, 32.8% yield). ₁H NMR (C6D6, 500 MHz) δ 7.93 (d,J=1.20 Hz, 2H), 7.63 (m, 12H), 7.42 (d, J=2.06 Hz, 2H), 7.28 (m, 7H),6.94 (dd, J=8.31, 2.06 Hz, 2H), 6.10 (d, J=8.31 Hz, 2H). ₁₃C NMR (C6D6,300 MHz) δ 149.68, 137.60, 136.23, 134.98, 134.90, 134.13, 133.78,133.12, 132.79, 131.41, 129.98, 128.57, 128.25, 127.89, 127.65, 126.88,126.52, 126.16, 125.62, 124.97, 124.82, 122.36, 114.73, 114.10. HRMS(ESI): calculated for M+ C₄₂H₂₇NO, 661.2405; observed 661.2413.

Synthesis of 3-(4-methoxyphenyl) Phenyl-10-Phenoxazine

3-bromo phenyl-10-phenoxazine (0.170 g, 0.502 mmol, 1.00 equiv.) and4-methoxyphenyl boronic acid (0.153 g, 1.00 mmol, 2.00 equiv.) wereadded to a storage tube and cycled between vacuum and nitrogen threetimes before 4.00 mL of dried and degassed THF was added. Once allreagents were dissolved, 4.00 mL of a 2.00 M aqueous solution of K₂CO₃,which had been sparged with nitrogen, was added. In a separate Schlenkflask, palladiumtetrakis(triphenyl phosphine) (0.0464 g, 0.0402 mmol,0.0800 equiv.) was dissolved in 4.00 mL of THF under inert atmosphere.The solution of Pd(PPh₃)₄ was then added to the reaction mixture and thereaction was heated at 100° C. for 48 h, before it was exposed to oxygenand allowed to cool to room temperature. The reaction mixture wasconcentrated under reduced pressure, diluted with DCM/hexanes, andpassed through a short plug of silica. The solution was then moved to aseparatory funnel, washed with de-ionized water once and brine twice.The solution was dried over magnesium sulfate, concentrated undervacuum, and recrystallized using DCM/methanol at −25° C. The product wascollected via vacuum filtration as a white solid (0.140 g, 0.378 mmol,76.0% yield). ₁H NMR (C₆D₆, 500 MHz) δ 7.37-7.31 (m, 2H), 7.13 (td,J=7.4, 6.7, 1.2 Hz, 2H), 7.07-7.01 (m, 1H), 7.00-6.94 (m, 2H), 6.83 (dd,J=7.8, 1.5 Hz, 1H), 6.80-6.76 (m, 3H), 6.54 (td, J=7.6, 1.5 Hz, 1H),6.46 (td, J=7.7, 1.5 Hz, 1H), 6.00 (d, J=8.3 Hz, 1H), 5.97 (dd, J=7.9,1.5 Hz, 1H), 3.31 (s, 3H). ₁₃C NMR (C₆D₆, 75 MHz) δ 159.08, 144.53,144.20, 139.25, 134.61, 134.46, 133.30, 132.77, 130.75, 130.69, 127.22,123.32, 121.45, 121.24, 115.63, 114.23, 113.92, 113.69, 113.44, 54.46.HRMS (ESI): calculated for M+ C₂₅H₁₉NO₂ 365.1416; observed 365.1418.

Synthesis of 3-(4-trifluoromethylphenyl) Phenyl-10-Phenoxazine

3-bromo phenyl-10-phenoxazine (0.170 g, 0.502 mmol, 1.00 equiv.) and4-methoxyphenyl boronic acid (0.191 g, 1.00 mmol, 2.00 equiv.) wereadded to a storage tube and cycled between vacuum and nitrogen threetimes before 4.00 mL of dried and degassed THF was added. Once allreagents were dissolved, 4.00 mL of a 2.00 M aqueous solution of K2CO3,which had been sparged with nitrogen, was added. In a separate Schlenkflask, palladiumtetrakis(triphenyl phosphine) (0.0464 g, 0.0402 mmol,0.0800 equiv.) was dissolved in 4.00 mL of THF under inert atmosphere.The solution of Pd(PPh₃)₄ was then added to the reaction mixture and thereaction was heated at 100° C. for 48 h, before it was exposed to oxygenand allowed to cool to room temperature. The reaction mixture wasconcentrated under reduced pressure, diluted with DCM, and passedthrough a short plug of silica. The solution was then moved to aseparatory funnel, washed with de-ionized water once and brine twice.The solution was dried over magnesium sulfate, concentrated undervacuum, and recrystallized using DCM/methanol at −25° C. The product wascollected via vacuum filtration as a white solid (0.0916 g, 0.378 mmol,45.0% yield). 1H NMR (C₆D₆, 500 MHz) δ 7.32 (d, J=8.1 Hz, 2H), 7.13 (dd,J=8.0, 6.2 Hz, 4H), 6.98 (d, J=2.0 Hz, 1H), 6.96-6.93 (m, 3H), 6.83 (dt,J=7.8, 1.2 Hz, 1H), 6.61 (dd, J=8.3, 2.0 Hz, 1H), 6.54 (tt, J=7.7, 1.2Hz, 1H), 6.46 (tt, J=7.8, 1.2 Hz, 1H), 5.97-5.91 (m, 2H). 13C NMR (C₆D₆,75 MHz) δ 144.58, 144.03, 143.36, 138.81, 134.68, 134.04, 132.70,130.86, 130.51, 128.62, 128.25, 128.20, 126.62, 126.16, 125.54, 123.50,121.93, 121.84, 115.62, 114.19, 113.60, 113.57.19F NMR (C6D6, 300 MHz) δ62.01. HRMS (ESI): calculated for M+ C25H16F3NO 403.1184; observed403.1184.

5,10-di(4-trifluoromethylphenyl)-5,10-dihydrophenazine radical

5,10-di(4-trifluoromethylphenyl)-5,10-dihydrophenazine was synthesizedaccording to established procedure. An oven-dried round bottom flask wascharged with 5,10-di(4-trifluoromethylphenyl)-5,10-dihydrophenazine(1.00 g, 2.13 mmol, 1.00 eq.), 400 mL of benzene, and a small magneticstir bar. Liquid bromine (403 mg, 2.55 mmol, 1.20 eq.) was added to theflask. A dark precipitate was observed almost immediately. The flask wassealed, vented, and left to stir overnight. The precipitate wascollected via vacuum filtration and rinsed with approximately 50 mL ofbenzene three consecutive times to afford an army green powder (1.12 g,96%). This powder was then dissolved in hot methanol, filtered, andplaced in a freezer. After three days, the solution was filtered toobtain 377 mg dark green crystals of 20. HRMS (ESI+): calc'd for M•+C₂₆H₁₆F₆N₂, 470.1218; found 470.1218. UV/Vis: λmax 481 nm (DMAc).E0=0.28 V vs. SCE (0.29 V vs. SCE reported for5,10-di(4-trifluoromethylphenyl)-5,10-dihydrophenazine).

3,7-Di(4-biphenyl) 1-Naphthalene-10-Phenoxazine, or3,7-di([1,1′-biphenyl]-4-yl)-10-(naphthalen-1-yl)-10H-phenoxazineradical

3,7-Di(4-biphenyl) 1-Naphthalene-10-Phenoxazine was synthesizedaccording to established procedure. An oven-dried round bottom flask wascharged with 3,7-Di(4-biphenyl) 1-Naphthalene-10-Phenoxazine (1.31 g,2.13 mmol, 1.00 eq.), 400 mL of benzene, and a small magnetic stir bar.Liquid bromine (10.2 g, 63.9 mmol, 30 eq.) was added to the flask. Thesolution immediately turned green with a precipitate was observed almostimmediately. The precipitate was filtered, then dissolved in DCM andprecipitated with ether 3 times.

(f) Copolymerization Experiments (Examples 1-6)

Synthesis of PMMA-b-PMMA

MMA (1.00 mL, 9.35 mmol, 1000 eq.), EBP (16.4 μL, 93.5 μmol, 10 eq.),and 3 (4.4 mg, 9.35 μmol, 1 eq.) were dissolved in 1.00 mL DMA andreacted according to the above general polymerization procedure for 12hours. At this time, an aliquot was taken for analysis (conv.=76.2%,M_(w)=14.3 kDa, Ð=1.21) and an additional 1.00 mL MMA and 1.00 mL DMAwere added to the reaction mixture. After an additional 6 h, theresulting polymer was isolated according to the above generalpolymerization procedure and analyzed (isol. yield=72%, %, Mw=40.7 kDa,Ð=1.16).

Synthesis of PMMA-b-PMMA with a Dark Resting Period

MMA (1.00 mL, 9.35 mmol, 1000 eq.), EBP (16.4 μL, 93.5 μmol, 10.0 eq.),and 3 (4.4 mg, 9.35 μmol, 1.00 eq.) were dissolved in 1.00 mL DMA andreacted according to the above general polymerization procedure for 8 h.At this time, an aliquot was taken for analysis (conv.=61.2%, Mw=12.0kDa, Ð=1.25). The reaction was then covered and left in the dark for 8h. At this time, an aliquot was taken for analysis (conv.=61.0%, Mw=12.0kDa, Ð=1.26) and an additional 1.00 mL MMA and 1.00 mL DMA were added tothe reaction mixture and irradiated. After 8 h, the resulting polymerwas isolated according to the above general polymerization procedure andanalyzed (isol. yield=70%, Mw=40.7 kDa, Ð=1.16).

Synthesis of PMMA-b-PMMA from Isolated Macroinitiator

MMA (130 μL, 1.20 mmol, 2000 eq.), a sample of isolated polymer fromTable 2, Run No. 11 (200 mg, 6.00 μmol, 10.0 eq.), and 3 (0.3 mg, 0.6μmol, 1.0 eq.) were dissolved in 0.87 mL DMA and reacted according tothe above general polymerization procedure for 12 h. The resultingpolymer was isolated according to the above general polymerizationprocedure and analyzed (isol. yield=62%, Mw=72.9 kDa, Ð=1.44).

Synthesis of PMMA-b-PBA with a Dark Resting Period

MMA (1.00 mL, 9.35 mmol, 1000 eq.), EBP (16.4 μL, 93.5 μmol, 10.0 eq.),and 3 (4.4 mg, 9.35 μmol, 1.00 eq.) were dissolved in 1.00 mL DMA andreacted according to the above general polymerization procedure for 8 h.At this time, an aliquot was taken for analysis (conv.=72.0%, Mw=13.7kDa, Ð=1.24). The reaction was then covered and left in the dark for 8h. At this time, an aliquot was taken for analysis (conv.=71.4%, Mw=13.3kDa, Ð=1.32) and an additional 1.30 mL BA and 1.00 mL DMA were added tothe reaction mixture. After 8 h, the resulting polymer was isolatedaccording to the above general polymerization procedure and analyzed(isol. yield=27%, Mw=84.5 kDa, Ð=1.33).

Synthesis of PMMA-b-PBA from Isolated Macroinitiator

BA (130 μL, 0.90 mmol, 2000 eq.), a sample of isolated polymer fromTable 2, Run No. 11 (150 mg, 4.50 μmol, 10.0 eq.), and 3 (0.23 mg, 0.45μmol, 1.00 eq.) were dissolved in 0.87 mL DMA and reacted according tothe above general polymerization procedure for 12 h. The resultingpolymer was isolated according to the general polymerization proceduredescribed above and analyzed (isol. yield=71%, Mw=92.9 kDa, Ð=1.38).

Synthesis of PMMA-b-PBnMA with a Dark Resting Period

MMA (1.00 mL, 9.35 mmol, 1000 eq.), EBP (16.4 μL, 93.5 μmol, 10.0 eq.),and 3 (4.4 mg, 9.35 μmol, 1.00 eq.) were dissolved in 1.00 mL DMA andreacted according to the above general polymerization procedure for 8 h.At this time, an aliquot was taken for analysis (conv.=66.0%, Mw=11.2kDa, Ð=1.34). The reaction was then covered and left in the dark for 8h. At this time, an aliquot was taken for analysis (conv.=66.0%, Mw=11.1kDa, Ð=1.34) and an additional 1.50 mL BnMA and 1.00 mL DMA were addedto the reaction mixture. After 8 h, the resulting polymer was isolatedaccording to the above general polymerization procedure and analyzed(isol. yield=69%, Mw=62.5 kDa, Ð=1.32).

Synthesis of PMMA-b-PBnMA from Isolated Macroinitiator

BnMA (150 μL, 0.90 mmol, 2000 eq.), a sample of isolated polymer fromTable 2, Run No. 11 (150 mg, 4.50 μmol, 10.0 eq.), and 3 (0.23 mg, 0.45μmol, 1.00 eq.) were dissolved in 0.85 mL DMA and reacted according tothe above general polymerization procedure for 12 h. The resultingpolymer was isolated according to the above general polymerizationprocedure and analyzed (isol. yield=81%, Mw=146.5 kDa, Ð=1.57).

General Experimental Procedure for the Polymerization of MethylMethacrylate Using Acridine-Based Compounds

A 20 mL disposable Scintillation vial was charged sequentially withN,N-dimethylacetamide (2 mL), methyl methacrylate (0.8 mL, 0.75 g, 7.5mmol), photocatalyst (0.1 mol %) under the atmosphere of N₂. After thephotocatalyst was dissolved, ethyl α-bromophenylacetate (13.1 pL, 0.075mmol) was introduced. The reaction was vigorously stirred in front ofwhite LEDs. Aliquots were taken and analyzed using ¹H NMR to give themolecular weight (Mn) and GPC to give the molecular weight distribution(Mw/Mn) of the polymer.

General Experimental Procedure for the Polymerization of MethylMethacrylate Using Coronene

Polymerizations were performed in a glovebox with a nitrogen atmosphere.A 20 mL vial was loaded with a stir bar and coronene, which wasdissolved in solvent, as specified in the polymerization tables. Theinitiator was added by syringe. This solution was allowed to stir for 1minute before 1 mL of the monomer was added at which point the timer wasstarted.

General Experimental Procedure for the Polymerization of MethylMethacrylate Using Perylene Derivatives

All polymerization reactions were conducted within a glove box under aNitrogen atmosphere in 20 mL scintillation vials. To a stirred solutionof a photocatalyst in the desired solvent, ethyl α-bromophenylacetate(EBP) followed by Methyl methacrylate (MMA) were added in the amountsspecified in the polymerization tables. The scintillation vial was thenplaced in the centre of a beaker of a 3 In. radius with a double layerof Flex LED strip of the desired wavelength surrounding the vial. Thepolymerizations were run for 24 hours with 0.1 mL aliquots taken everyhour for the first 5 hours and at 24 hours. Each aliquot was quenched ina seal vial containing 0.7 mL CDCl₃ with 250 ppm of BHT. An ¹H NMR wastaken to track the conversion prior to removing the volatiles andredissolving the residues in THF for GPC analyses.

(g) Computational Details (Examples 1-7)

Standard reduction potentials (E⁰) were calculated following previouslyreported procedures (Tossell, 2011, Comput. Theor. Chem. 977:123-127;Winget, et al., 2004, Theor. Chem. Acc. 112:217-227; He, et al., 2010,J. Phys. Chem. C. 114:21474-21481; Zhao & Truhlar, 2008, Theor. Chem.Acc. 120:215-241).

A value of −100.5 kcal/mol was assumed for the reduction free energy ofthe standard hydrogen electrode (SHE). Thus, E⁰=(−100.5−ΔG_(red))/23.06(V vs. SHE); for E⁰ (³PC*/PC^(⋅+)), ΔG_(red)=G(³PC*)−G(PC⁺) while for E⁰(PC^(⋅+)/PC), ΔG_(red)=G(PC)−G(PC^(⋅+)). The Gibbs free energies of³PC*, PC^(⋅+), and PC were calculated at the unrestricted M06/6-31+G**level of theory in CPCM-H₂O solvent. To reference to the SaturatedCalomel Electrode (SCE), E⁰ (vs. SHE) is converted to E⁰ (vs. SCE) usingE⁰ (vs. SCE)=E⁰ (vs. SHE)−0.24 V. Triplet energies (in eV) of PCs wereobtained by [G(³PC*)−G(PC), in kcal/mol]/23.06.

Population analysis was performed using electrostatic potential-derivedcharges with the CHELPG methods performed at the unrestrictedM06/6-31G** level of theory in CPCM-H₂O solvent.

Geometry optimization of PC (3,7-Di(4-biphenyl)1-Naphthalene-10-Phenoxazine) was performed at the unrestrictedM06/Lanl2dz level of theory in CPCM-H₂O solvent; the smaller Lanl2dzbasis sets was employed for computational efficiency due to itsextensive structure. Singlet point calculation at the convergedM06/Lanl2dz geometry was then performed at the unrestricted M06/6-31+G**level of theory in CPCM-H₂O solvent.

(h) Experimental Conditions for Example 7:

Control Experiments

Control polymerizations revealed negligible or no polymerization in theabsence of any of the components pertinent to the O-ATRP system (light,PC, or initiator) or in the presence of oxygen.

General Procedure for O-ATRP of MMA Using a UV Light Source

A 20 mL scintillation vial equipped with a small stirbar was transferredinto a nitrogen-atmosphere glove box. To this vial DMA, methylmethacrylate (MMA), photocatalyst from a stock solution in DMA andinitiator were added in that order via pipette. The vial was tightlysealed and wrapped in aluminum foil. The vial was transferred out of theglove box, the aluminum foil was removed, then placed under UVirradiation while stirring (FIGS. 26A-26D). Timing of the polymerizationstarted once the vial was placed under irradiation. To analyze theprogress of the polymerization at a given time point, aluminum foil waswrapped around the vial, the timer was stopped and the sample was takenback into the glove box where a 0.1 mL aliquot of the reaction wasremoved via syringe and injected into a vial containing 0.7 mL CDCl₃with 250 ppm butylated hydroxytoluene (BHT) to quench the reaction. Thereaction vessel was then transferred back under UV irradiation where thetimer was once again started. This aliquot was then analyzed via NMR forconversion. After NMR, the volatiles were removed from the sample,redissolved in THF and passed through a syringe filter for analysis bygel permeation chromatography coupled with multi-angle light scattering.

Monomer Scope

The polymerization of different monomers—BMA, BnMA and DMA—were carriedout using the general polymerization conditions described above. A ratioof [1000]:[10]:[1], [monomer]:[initiator]:[catalyst] was used with 9.35mmol of monomer used in each trial. An equal volume of DMA to monomerwas used. After the polymerization was allowed to run for 8 hours analiquot was taken for analysis of monomer conversion by ¹H NMR, afterwhich, methanol was immediately added to the reaction mixture toprecipitate out the polymer. The resulting solid polymer was filteredthen dried and used for analysis by gel permeation chromatographycoupled with multi-angle light scattering. The results from thesepolymerizations are given in Table 12.

General Procedure for Chain Extension of Poly Methyl Methacrylate withVarious Monomers by Photocatalyzed O-ATRP

Synthesis of PMMA Macroinitiator

Catalyst 3 (23.2 mg, 0.0748 mmol, 8 eq.) was dissolved in 8.00 mL DMAand stirred with MMA (8.00 mL, 74.8 mmol, 1000 eq.), and DBMM (143 μL,0.748 mmol, 10 eq.) in a 20 mL scintillation vial in a nitrogen-filledglove box. The reaction mixture was then wrapped in aluminum foil,removed from the glove box and placed into the aforementioned UVapparatus. The reaction ran for 4 hours before the reaction media waspoured into 800 mL of stirring room temperature methanol. The resultingpolymer was stirred for an hour before being dissolved in a minimalamount of dichloromethane. The polymer was dissolved withdichloromethane and re-precipitated into stirring methanol a total ofthree times to remove unreacted monomer, initiator or catalyst (Mn=8.83kDa, Mw=9.85 kDa, Ð=1.12).

Synthesis of Block Copolymers from Isolated Macroinitiator

Block copolymers were synthesized using a ratio of [1500]:[10]:[1],[monomer]:[initiator]:[catalyst] using 0.100 g of macroinitiator in eachtrial, and catalyst 3. Each reaction was set up using the same method asthe general polymerization procedure described above. Thepolymerizations were all run for 10 hours before the reaction media waspoured into 100 mL of stirring, room temperature methanol. The resultingpolymers were collected via vacuum filtration and dried under vacuum.The results from these polymerizations are given in Table 13.

General Procedure for O-ATRP of MMA Using a Visible Light Source

A 20 mL scintillation vial equipped with a small stirbar was transferredinto a nitrogen-atmosphere glove box. To this vial DMA, methylmethacrylate (MMA), photocatalyst from a stock solution in DMA andinitiator were added in that order via pipette. Timing of thepolymerization started once the vial was placed into an LED-lined beaker(FIG. 5). To analyze the progress of the polymerization at a given timepoint, a 0.1 mL aliquot of the reaction was removed via syringe andinjected into a vial containing 0.7 mL CDCl₃ with 250 ppm butylatedhydroxytoluene (BHT) to quench the reaction. This aliquot was thenanalyzed via NMR for conversion. After NMR, the volatiles were removedfrom the sample, redissolved in THF and passed through a syringe filterfor analysis by gel permeation chromatography coupled with multi-anglelight scattering.

Characterization photoredox properties of certain catalysts in Example 7are illustrated in FIGS. 30A-30D, 31-32, 33A-33E, 34 and 35A-35B.

In non-limiting examples, the polymerization of methyl methacrylate wasdemonstrated using the various dyes as organic photocatalysts andethyl-α-bromophenylacetate as the initiator. The results are illustratedherein.

Example 1: Representative Results of the Polymerization of MethylMethacrylate Using Phenazine Dyes

The results are summarized in Tables 1-2. The results represent thatthese organic molecules can serve as organic photocatalysts that operatethrough an oxidative quenching pathway in the polymerization of methylmethacrylate. A controlled radical polymerization was mediated by the CNfunctionalized diphenyl phenazine, as evidenced by the linear increasein polymer molecular weight and constant dispersity as a function ofmonomer conversion (FIG. 16). A first-order dependence on monomerconversion as a function of time was observed (FIG. 17). The y-interceptof the Mn vs. conversion plot was 3.46 kDa, suggesting an uncontrolledchain-growth period adding ˜32 MMA equivalents during the onset ofpolymerization before precise control is attained; whereas, an idealpolymerization would have a y-intercept equal to the mass of theinitiator (MW of EBP=243 Da).

Example 2: Representative Results of the Polymerization of MethylMethacrylate Using Acridine Dyes as Photocatalysts

The results are summarized in Table 5.

TABLE 5 Representative Results for the Polymerization of MethylMethacrylate Acridine Dyes. conversion M_(w) M_(n) D entry catalystlight source solvent time (%) (kDa) (kDa) (M_(w)/M_(n)) I* 7 5 white LEDDMAc 1 h 17.5 50.6 23.2 1.75 7.56 8 6 white LED DMAc 1 h 10.5 62.9 41.81.51 8.87 9 7 white LED DMAc 1 h 17.2 21.6 11.1 1.94 15.5 10 8 365 nmDMAc 1 h 5.4 12.7 7.7 1.70 5.40 11 9 365 nm DMAc 1 h 60.0 20.4 16.8 1.2135.7 12 10 365 nm DMAc 1 h 29.9 31.3 15.4 2.00 19.4 13 11 365 nm DMAc 1h 15.9 21.6 11.2 1.60 14.3 Conversion measured by ¹H NMR. Molecularweight and dispersity measured by gel-permeation chromatography coupledwith a light-scattering detector. Initiator efficiency (/*) =theoretical molecular weight/experimental number average molecularweight * 100.

Example 3: Representative Results of the Polymerization of MethylMethacrylate Using Coronene

The results are summarized in Table 6.

TABLE 6 Representative Results for the Polymerization of MethylMethacrylate Using Coronene as a Phototocatalyst. solvent light volumeconversion M_(w) M_(n) D entry source solvent (mL) time (%) (kDa) (kDa)(M_(w)/M_(n)) I* 14 white LED DMAc 4 1 h 19.5 47 37 1.27 5.4 14 whiteLED DMAc 4 2 h 33.7 46 38 1.19 9.0 14 white LED DMAc 4 4 h 52.4 47 411.13 13.1 14 white LED DMAc 4 7 h 67.2 55 51 1.08 13.6 14 white LED DMAc4 12 h  79.2 63 59 1.06 13.7 14 white LED DMAc 4 24 h  91.5 73 70 1.0413.4 Ratio: [MMA]:[EBP]:[coronene] = 1000:10:4; 1.0 ml MMA. Conversionmeasured by ′H NMR. Molecular weight and dispersity measured bygel-permeation chromatography coupled with a light-scattering detector.Initiator efficiency (/*) = theoretical molecular weight/experimentalnumber average molecular weight * 100.

Example 4: Representative Results of the Polymerization of MethylMethacrylate Using Perylene Dyes

The results are summarized in Table 7.

TABLE 7 Representative Results for the Polymerization of MethylMethacrylate Using Perylene Dyes as Phototocatalysts. light conversionentry Catalyst source solvent time (%) M_(w) (kDa) M_(n) (kDa) D(M_(w)/M_(n)) I* 15 12B violet LED DMAc 2 h 20.3 14.9 10.6 1.4 19.2 1612D violet LED DMAc 2 h 17.4 19.9 13.4 1.50 13.0 17 12E violet LED DMAc2 h 20.9 27.9 10.9 2.60 19.21 18 12G violet LED DMAc 2 h 10.2 209 97.42.15 1.04 19 12F violet LED DMAc 2 h 29.8 60.5 24.8 2.40 12.0 20 12Aviolet LED DMAc 2 h 20.8 15.4 9.3 1.60 19.5 Conversion measured by ¹HNMR. Molecular weight and dispersity measured by gel-permeationchromatography coupled with a light-scattering detector. Initiatorefficiency (I*) = theoretical molecular weight/experimental numberaverage molecular weight * 100.

Example 5

Polymerization data, including information for PCs 1, 2, 4, and 5, andan initiator screen for PCs 3 and 6. Polymerizations were performedaccording to the above general polymerization procedure using 9.35 mmol(1000 eq.) monomer, 9.35 μmol (1 eq.) catalyst, and 93.5 μmol initiator.

Run Ð No. PC Initiator DMA Time (h) Conv. (%) M_(w) M_(n) (M_(n)/M_(w))I* S1 1 EBP 1 mL 8 69.6 36.3 24.7 1.47 29.2 S2 2 EBP 1 mL 8 85.9 18.411.9 1.55 74.5 S3 4 EBP 1 mL 8 73.5 21.4 16.1 1.33 47.2 S4 4 EBP 1 mL 736.7 9.63 7.47 1.29 52.5 S5 3 MBriB 1 mL 8 94.0 18.8 15.0 1.25 63.5 S6 3MBP 1 mL 8 86.0 9.80 7.37 1.33 118 S7 3 EClP 1 mL 4 96.0 21.9 8.62 2.54111 S8 5 EBP 1 mL 5 39.4 9.35 9.08 1.03 46.1 S9 6 EBP 1 mL 5 54.1 12.311.4 1.08 47.5 S10 6 BrPN 2 mL 8 73.3 15.8 12.8 1.24 58.1 S11 6 EClP 2mL 8 93.7 24.3 18.0 1.35 53.2 S12 6 MBriB 2 mL 8 90.2 14.4 10.7 1.3585.9

Example 6

Monomer scope of catalysts 3 and 6. Polymerizations were performedaccording to the above general polymerization procedure using 9.35 mmol(1000 eq.) monomer, 9.35 μmol (1 eq.) catalyst, 93.5 μmol initiator, and1.00 mL DMA.

Ð Run Initi- Conv. (M_(n)/ No. PC Monomer ator (%) M_(w) M_(n) M_(w)) I*S13 3 TMSHEMA EBP 83.3 25.3 20.0 1.26  85.5 S14 3 TFEMA EBP 77.4 58.254.7 1.06  24.2 S15 3 DEGMA EBP 94.7 30.1 21.3 1.41  84.6 S16 3 BA EBP98.5 26.6 16.4 1.62  60.0 S17 3 St EBP  0.0 n/a n/a n/a n/a S18 3 VA EBP 0.0 n/a n/a n/a n/a S19 3 AN EBP 71.3 40.3* 23.7* 1.70  15.6 S20 6TMSHEMA MBP 90.8 18.7 16.0 1.17 116 S21 6 TFEMA MBP 79.4 53.9 32.9 1.64 41.3 S22 6 DEGMA MBP 92.6 22.8 18.4 1.24  96.0 S23 6 BA MBP 99.9 30.121.2 1.42  60.3 S24 6 BnMA MBP 96.6 53.4 43.1 1.24  79.0

Example 7: Organocatalyzed Atom Transfer Radical Polymerization UsingN-Aryl Phenoxazines as Photoredox Catalysts

Although controlled radical polymerizations exist that are mediated byorganic catalysts and which thus entirely circumvent the issue of metalcontamination, organic catalysts capable of mediating an organocatalyzedATRP (O-ATRP) are limited because of the required significant reducingpower required to reduce alkyl bromides commonly used for ATRP (˜−0.6 to−0.8 V vs SCE).

Photoredox catalysis presents a strategy to drive chemicaltransformations under mild conditions through the generation of reactiveopen-shell catalysts via photoexcitation. However, most photoredoxcatalysts (PCs) do not possess the reducing power to directly reduce analkyl bromide through an outer sphere electron transfer mechanism.Strongly reducing organic catalysts, including perylene, N-arylphenothiazines, and N,N-diaryl dihydrophenazines have been demonstratedas organic PCs capable of mediating O-ATRP (FIGS. 23A-23C). Continuedprogress in this field is required to further understand the mechanismof this polymerization to realize even more efficient PCs and access abroader application landscape.

A proposed general photoredox O-ATRP mechanism involves photoexcitationof the PC to an excited state PC (PC*) that is capable of reducing alkylbromides via an oxidative quenching pathway to generate the activeradical for polymerization propagation, while yielding the radicalcation PC (PC^(⋅+)) and Br⁻ ion pair complex, PC^(⋅+)Br⁻ (FIG. 23C).Efficient deactivation is important to the production of well-definedpolymers. Deactivation requires the PC^(⋅+)Br⁻ complex to besufficiently oxidizing relative to the propagating radical to regeneratethe alkyl bromide and ground state PC; subsequent photoexcitation of thePC reinitiates the catalytic cycle. The present studies demonstrate thatN-aryl phenoxazines are a new class of PCs for O-ATRP, producingwell-defined polymers with low dispersities. The present studies providea visible light phenoxazine PC that produces polymers with Ð rangingfrom 1.13 to 1.31 over a range of polymer MWs while achievingquantitative initiator efficiency (I*).

In certain embodiments, photoexcitation of the PC delivers—throughintersystem crossing (ISC) from the singlet excited state PC (¹PC*)—atriplet excited state PC (³PC*), which is responsible for the alkylbromide reduction. In other embodiments, the photoexcited speciespossesses a sufficiently long lifetime for photoredox catalysis.

Reported elsewhere herein are strong excited state reduction potentials(E⁰*=E⁰(²PC^(⋅+)/PC*)) of N,N-diaryl dihydrophenazines and N-arylphenothiazines (˜−2 V vs SCE), which are even more reducing thancommonly used metal PCs, such asfac-Ir(ppy)₃ (−1.73 V vs SCE). Incertain embodiments, N-aryl phenoxazines are also a class of organic PCsfor O-ATRP.

DFT calculations predict that N-aryl phenoxazines possess similarlystrong E⁰*s (˜−2 V vs. SCE) in their lowest lying triplet excited stateas dihydrophenazines and phenothiazines. Although dihydrophenazines arestronger excited state reductants, the radical cations of phenoxazinesand phenothiazines [E⁰(²PC^(⋅+)/PC)=˜0.5 V vs SCE] are more oxidizingthan those of dihydrophenazines [E⁰(²PC^(⋅+)/PC)=˜0.0 V vs SCE]; allthree classes of PCs possess an oxidation potential capable ofdeactivating the propagating radical (e.g. ˜−0.8 V vs SCE for methylmethacrylate), as required for a successful O-ATRP. Lastly, thephosphorescence quantum yield of 10-phenylphenoxazine (1) at 77 K is 94%with a lifetime as long as 2.3 seconds. These properties highlight theefficient ISC to the triplet manifold and slow non-radiative decayattributed to small Franck-Condon vibrational overlap factors between³PC* and the ground state.

The analysis of exchanging the sulfur in phenothiazines with the oxygenin phenoxazines identified several distinct phenomena that alter thephysical properties of these molecules and which manifest inimprovements in PC performance for O-ATRP, qualitatively assessedthrough analysis of the polymer product. One distinction between thesetwo systems is the conformation of their heterocyclic rings. The smallervan der Waals radius of oxygen (1.52 Å) relative to sulfur (1.80 Å)permits the ground state phenoxazine (e.g. PC 1) to access a planargeometry similarly to dihydrophenazines (nitrogen, 1.55, Å). Incontrast, phenothiazine adopts a bent boat conformation in its groundstate, observable in crystal structures and predicted by the presentlyperformed computations (FIG. 24). However, upon oxidation to the radicalcation state ²PC^(⋅+), all three PCs adopt a planar conformation.

The consequences of phenothiazine adopting bent conformations in theground and triplet states, but a planar geometry in the radical cationstate, introduce larger structural reorganizations during electrontransfer (ET) as compared to the isoelectronic, but consistently planar,phenoxazines and dihydrophenazines. A structural reorganization penaltyassociated with oxidation of the bent 10-phenylphenothiazine tripletstate to the planar radical cation was calculated to be 8.2 kcal/mol. Incontrast, the triplet and radical cation states of 1 are bothplanar—analogous to diaryl dihydrophenazines—which results in a lowerreorganization energy of only 2.4 kcal/mol. As phenoxazine,dihydrophenazine, and phenothiazine derivatives possess similar E⁰*s(−2.20 V, −2.34 V, and −2.10 V, respectively), a kinetically fasteractivation (reduction of the alkyl bromide) in O-ATRP by phenoxazinesand dihydrophenazines is expected because of their lower reorganizationenergies for ET.

Polymerization deactivation involves reduction of the planarphenylphenothiazine radical cation to regenerate the bent ground state.A reorganization energy for this ET was calculated as being 4.1kcal/mol. For 1 or diphenyl dihydrophenazine, the same reduction processrequires lower reorganization energies of 2.3 or 2.5 kcal/mol,respectively consistent with the conservation of the planarity of thecation radical and ground states. Given the similar ground stateoxidation potentials for the phenoxazine and phenothiazine (0.50 and0.43 V), the radical cation of 1 is likely kinetically faster indeactivation, which imparts better control in O-ATRP (vide infra).

Studies described elsewhere herein revealed that PCs with spatiallyseparated singly occupied molecular orbitals (SOMOs) in their ³PC* stateyielded PCs with superior performance in O-ATRP in regards to achievingthe highest I* and producing polymers with the lowest Ð. As such,strongly reducing N-aryl phenoxazines with spatially separated SOMOs(with the lower lying SOMO localized on the phenoxazine core and thehigher lying SOMO localized on the aryl substituent) and localized SOMOs(with both SOMOs localized on the phenoxazine core) were investigated toevaluate their performance as O-ATRP PCs and determine if this conceptextends to phenoxazines (FIGS. 25A-25B).

In the cases of diphenyl dihydrophenazine and 1, it was calculated thatneither exhibits spatially separated SOMOs. In contrast, incorporationof electron withdrawing trifluoromethyl functionalization on the paraposition of the N-phenyl substituents of the dihydrophenazine yieldedspatially separated SOMOs whereas this substitution on phenoxazine (2)results in both SOMOs localized on the phenoxazine core. However, forboth dihydrophenazines and phenoxazines, N-aryl functionalization(s)with 1- or 2-naphthalene yielded molecules with spatially separatedSOMOs, and thus predicted intramolecular charge transfer from theheterocyclic ring to the naphthalene substituent upon photoexcitationand subsequent intersystem crossing to the triplet state.

All four phenoxazine derivatives were synthesized through C—Ncross-couplings from commercially available reagents and employed in thepolymerization of MMA. A screen of common ATRP alkyl bromide initiatorsrevealed that diethyl 2-bromo-2-methylmalonate (DBMM) served as thesuperior initiator to produce polymers with the lowest Ð while achievingthe highest I* (Table 14). To evaluate the PCs, polymerizations usingDBMM as the initiator were conducted in dimethylacetamide and irradiatedwith a 365 nm UV nail curing lamp (54 watts) (Table 8). In accord withdiaryl dihydrophenazines, N-aryl phenoxazines possessing localized SOMOs(PCs 1 and 2) did not perform as well as the PCs with separated SOMOs(PCs 3 and 4). Specifically, 1 and 2 produced poly(methyl methacrylate)(PMMA) with a relatively high Ð of 1.48 and 1.45, respectively (runs 1and 2). Polymerization results with PCs 3 and 4 were superior, andproduced PMMA with lower dispersities (Ð=1.22 and 1.11, respectively)while achieving high I*s of 92.6 and 77.3%, respectively (runs 3 and 4).

TABLE 8 Results of the O-ATRP of MMA using PCs 1 through 4.^(a) Conv.M_(w) M_(n) Dispersity I* Run No. PC (%) (kDa) (kDa) (Ð) (%) 1 1 95.610.6 7.2 1.48 137 2 2 55.3 9.5 6.5 1.45 85.5 3 3 78.8 10.8 8.8 1.22 92.64 4 80.2 11.9 10.8 1.11 77.3 ^(a)[MMA]:[DBMM]:[PC] = [1000]:[10]:[1];9.35 μmoles PC, 1.00 mL dimethylacetamide, and irradiated with a 54 watt365 nm light source for 8 hours.

Further, molecular weight control could be obtained using either PCthrough modulation of the monomer (runs 5 to 9 for PC 3; runs 13 to 17for PC 4) or initiator (runs 10 to 12 for PC 3; runs 18 to 20 for PC 4)ratios (Table 9). Overall, PC 3 produced PMMA through higher I*(˜80-100%) while PC 4 produced PMMA with lower Ð (as low as 1.07). This1-naphthalene versus 2-naphthalene substitution effect influencing highI* or low Ð, respectively was also observed with diaryldihydrophenazines.

Our analysis of the polymerization of MMA by 3 and 4 showed that bothPCs imparted control over the polymerization that is becoming expectedfrom O-ATRP. Specifically, a linear growth in polymer molecular weightas well as a low dispersity during the course of polymerization wasattained (FIG. 26, Panels A-B). Additionally, temporal control wasdemonstrated using a pulsed irradiation sequence (FIG. 26, Panels C-F).Monomer conversion was only observed during irradiation, which resultedin a linear increase in number-average MW (M_(n)) while producing PMMAwith low Ð.

TABLE 9 Results of the O-ATRP of MMA using PCs 3 and 4. Run ConversionM_(w) M_(n) Dispersity I* No. PC [MMA]:[DBMM]:[PC] (%) (kDa) (kDa) (Ð)(%) 5 3 [500]:[10]:[1] 80.8 5.8 4.9 1.16 86.1 6 3 [1000]:[10]:[1] 78.810.8 8.8 1.22 92.6 7 3 [1500]:[10]:[1] 72.2 11.4 9.5 1.19 116 8 3[2000]:[10]:[1] 76.5 18.4 14.6 1.26 107 9 3 [2500]:[10]:[1] 78.4 25.919.8 1.31 101 10 3 [1000]:[5]:[1] 74.6 26.4 19.1 1.38 79.6 11 3[1000]:[15]:[1] 74.5 8.3 6.9 1.20 75.7 12 3 [1000]:[20]:[1] 80.7 5.5 4.61.19 92.9 13 4 [500]:[10]:[1] 85.1 5.9 5.4 1.09 84.1 14 4[1000]:[10]:[1] 80.2 11.9 10.7 1.11 77.3 15 4 [1500]:[10]:[1] 68.9 12.29.8 1.25 109 16 4 [2000]:[10]:[1] 58.2 14.7 112.5 1.17 95.2 17 4[2500]:[10]:[1] 65.9 21.2 17.3 1.23 96.6 18 4 [1000]:[5]:[1] 70.5 22.316.8 1.35 85.3 19 4 [1000]:[15]:[1] 70.9 9.3 8.3 1.12 60.6 20 4[1000]:[20]:[1] 76.1 6.8 6.1 1.07 64.0

Both PCs also efficiently polymerized other methacrylates, includingbenzyl methacrylate (BnMA), isobutyl methacrylate (BMA), and isododecylmethacrylate (IDMA) (Table 12). As such, 3 was used to perform chainextension polymerizations from an isolated PMMA (M_(w)=9.9 kDa, Ð=1.12)macroinitiator because the ATRP mechanism inherently reinstalls thebromine chain end group onto the growing polymer chain (FIG. 27). Chainextensions from this PMMA macroinitiator with MMA, DMA, BnMA, and BMAwere successful, both confirming high bromine chain end group fidelityand allowing the synthesis of block polymers.

To further establish these naphthalene phenoxazines as efficient PCs, 3and 1-napthylene-10-phenothiazine were directly compared as PCs forO-ATRP under the polymerization conditions (FIGS. 37A-37B). Bothcatalysts exhibited nearly identical rates of polymerization, achieving85.1% and 88.4% monomer conversion after 10 hours for 3 and thephenothiazine, respectively. Additionally, both PCs achieved high I*s of93.5% and 95.6%, respectively. However, a significant difference inpolymerization performance was observed when comparing the Ð of theresulting PMMA. When using 3, PMMA was produced with Ð=1.26, while thephenothiazine produced PMMA with comparatively higher Ð=1.66.

As inferred above, the higher Ð of the PMMA produced by thephenothiazine is attributed to the larger reorganization energies of thephenothiazines. Incorporation of O versus S in the core of phenoxazinesversus the core of phenothiazines imparts distinct quantitativedifferences in the electronic and geometric structures of thesemolecules that affect their performance as PCs for O-ATRP. As such, theplanarity of phenoxazines throughout the photoexcitation and ETprocesses causes them to perform more closely to diaryldihydrophenazines as PCs for O-ATRP. Without wishing to be limited byany theory, differences between these PCs specifically manifest in eachof their abilities to balance the rates of activation and deactivation,which results in differences observed in the Ð of the resulting PMMAproduced by each PC.

An additional consideration when comparing phenoxazines,dihydrophenazines, and phenothiazines is that the planar core ofphenoxazines and dihydrophenazines promotes intramolecular chargetransfer to charge separated SOMOs while the bent phenothiazine corelimits electronic coupling between the heterocyclic ring and the N-arylsubstituent and consequently the ability to form an intramolecularcharge transfer complex. The planar phenoxazine core versus the bentphenothiazine core can be visualized in the X-ray crystal structures ofthe PCs (FIGS. 28A-28B). The electrostatic potential (ESP) mappedelectron density of the ³PC* state of these compounds reveal thatelectron density is transferred to the naphthalene substituent (redregion) in phenoxazine upon photoexcitation and ISC, even more so withdihydrophenazines, while electron density remains localized on thephenothiazine core (FIGS. 29A-29C).

In certain embodiments, a visible light absorbing phenoxazine derivativeprovides an even more efficient polymerization catalyst, as irradiationof the reaction with high energy UV-light can initiate non-desirablereaction pathways, which may increase the Ð of the produced polymer andlower I*. To realize a visible light absorbing PC, a core substitutedphenoxazine derivative was explored. Computations predicted that PC 5,possessing 4-biphenyl core substitutions, would be an excellent targetPC with ³PC* possessing a strong reduction potential and spatiallyseparated SOMOs, while ¹PC would exhibit an absorbance profile in thevisible spectrum. The visible light absorbing PC 5 was synthesized inhigh yield from PC 3 through selective bromination at the 3- and7-positions on the phenoxazine core using N-bromosuccinimide followed bySuzuki cross-coupling. The absorbance profile of PC 5 was not onlyred-shifted (Δλ_(max)=65 nm versus non-core substituted PC 3) into thevisible spectrum (λ_(max)=388 nm), but also exhibited an extremelyenhanced molar extinction coefficient (ε=26635 M⁻¹cm⁻¹ at λ_(max)=388nm), making it significantly more efficient at absorbing visible lightthan the non-core substituted 1-napthalene functionalized phenoxazine,dihydrophenazine, or phenothiazine (FIGS. 30A-30D).

The polymerization performance of PC 5 indicated that it is an excellentPC for O-ATRP, demonstrating superior control over the polymerizationthan the UV-absorbing phenoxazines or even previously reporteddihydrophenazines. The polymerization of MMA using PC 5 irradiated bywhite LEDs was efficient and showcased characteristics of a controlledpolymerization with a linear increase in polymer M_(n) and a low polymerÐ during the course of polymerization (FIG. 30C). Furthermore, themolecular weight of the polymer can be tailored through manipulation ofeither the monomer or initiator loading, while keeping thepolymerization otherwise constant, to produce polymers with Ð of1.13-1.31 while achieving quantitative I* (Table 10).

TABLE 10 Results of the O-ATRP of MMA using PC 5 Con- Run version M_(w)M_(n) Dispersity I* No. [MMA]:[DBMM]:[5] (%) (kDa) (kDa) (Ð) (%) 21[500]:[10]:[1] 67.2 4.07 3.64 1.13 99.4 22 [1500]:[10]:[1] 75.2 13.711.8 1.16 98.0 23 [2000]:[10]:[1] 90.9 22.9 17.5 1.31 105 24[2500]:[10]:[1] 87.5 27.5 21.3 1.29 104 25 [1000]:[5]:[1] 89.9 23.0 18.11.27 101 26 [1000]:[15]:[1] 73.8 6.17 5.31 1.16 97.5 27 [1000]:[20]:[1]72.1 4.52 3.76 1.20 103

N-aryl phenoxazines have proven to be efficient PCs for O-ATRP thatproduce polymers with controlled molecular weights and low dispersity.Through the culmination of computational and experimental results, thepresent studies provide a visible light absorbing phenoxazine photoredoxcatalyst that produces polymers with controlled molecular weights andlow dispersities, achieving quantitative initiator efficiencies thatoutcompete previously reported organic PCs for O-ATRP. The continuedestablishment of design principles for PCs capable of mediating O-ATRPhelps expand the scope and impact of this polymerization methodology,which allows for an additional means for selective small moleculetransformations.

TABLE 11 Calculation of excited state reduction potentials ofphotocatalysts 1-5 (Example 1) E(em em λ_(max)) E(triplet), abs λ_(max)ε_(λmax) λ_(max) (V vs. theo (V PC (nm)^(a) (M⁻¹cm⁻¹)^(b) (nm)^(c)SCE)^(d) vs. SCE)^(e) 1 324 7729 392 3.16 2.69 2 322 6719 504 2.46 2.633 323 7848 524 2.37 2.39 4 318 8047 509 2.44 2.45 5 388 26635 506 2.452.41 E_(1/2) E⁰ E⁰* E⁰* (PC^(•+)/PC) (PC^(•+)/PC), (PC^(•+)/PC*)(PC^(•+)/³PC*), (V theo (V (V theo (V PC vs. SCE) vs. SCE)^(e) vs. SCE)vs. SCE)^(e) 1 0.74 0.50 −2.42^(f) −2.20 2 0.80 0.51 −1.66 −2.12 3 0.760.47 −1.61 −1.92 4 0.74 0.47 −1.70 −1.98 5 0.70 0.40 −1.75 −2.01^(a)Maximum absorption wavelength; PC 3 and 4 exhibit another λ_(max) athigher energy wavelengths of 283 nm and 278 nm, respectively. ^(b)Molarabsorptivity at the reported λ_(max). ^(c)Maximum emission wavelengthwhen irradiated with 320 nm light (PC 1-4) and 380 nm light (PC 5).^(d)Energy of emitted photons. ^(e)Theoretical predictions from DFTcalculations at uM06/6-31 + Gdp/CPCM-H₂O level of theory. ^(f)The E0* ofPC 1 is significantly more negative than PC 2-5 and deviates from thepredicted trend. In the DFT calculations, the triplet excited state wasexplicitly assumed while the observed emission is likely fluorescencefrom the relaxed singlet excited state.

TABLE 12 Polymerization Results of O-ATRP of Methacrylates.^(a) 3

4

Time Conv M_(n) M_(w) Ð I* PC Monomer (h) (%) (kDa) (kDa) (M_(w)/M_(n))(%) 3 BMA 8 62.0 13.5 16.4 1.22 67.4 3 BnMA 8 46.1 8.2 11.6 1.41 102 3DMA 8 87.5 20.9 28.3 1.35 42.9 4 BMA 8 62 15.2 17.3 1.14 59.7 4 BnMA 877.1 12.5 16.0 1.28 110 4 IDMA 8 83.2 21.7 28.4 1.31 39.6^(a)Polymerizations of vinyl monomers were performed at [1000]:[10]:[1]using DBMM as the initiator and the same volume of solvent as that ofthe monomer added.

TABLE 13 Polymerization Results of O-ATRP PMMA chain extensions.^(a)M_(n) M_(w) Ð PC Monomer A Monomer B Time (h) (kDa) (kDa) (M_(w)/M_(n))3 MMA MMA 10 38.8 49.4 1.27 3 MMA BMA 10 38.8 43.8 1.13 3 MMA IDMA 1059.8 77.6 1.29 3 MMA BnMA 10 46.8 67.1 1.43 ^(a)Polymerization chainextensions were performed at [1500]:[10]:[1] using a PMMA macroinitiatorand the same volume of solvent as that of the monomer added.

TABLE 14 Polymerization Results of O-ATRP initiator screen for PC1-4.^(a) 1

2

3

4

Time Conv Ð I* PC Initiator (h) (%) M_(n)(kDa) M_(w)(kDa) (M_(w)/M_(n))(%) 1 EBP 8 92.2 8.01 14.3 1.79 119 1 DBMM 8 95.6 7.16 10.6 1.48 137 2EBP 8 61.2 15.4 20.7 1.34 41.2 2 DBMM 8 55.3 6.54 9.48 1.45 85.5 3 EBP 866.4 9.29 12.6 1.36 74.2 3 MBiB 8 76.5 9.58 11.8 1.23 81.8 3 MBP 8 70.710.9 14.1 1.29 66.4 3 DBMM 8 78.8 8.79 10.8 1.22 92.6 4 EBP 8 59.0 11.313.6 1.21 54.7 4 MBiB 8 69.2 11.3 15.0 1.34 63.3 4 MBP 8 31.7 5.80 6.871.19 57.6 4 DBMM 8 80.2 10.7 11.9 1.11 77.3 ^(a)Polymerizations wereperformed at [1000]:[10]:[1] for [MMA]:[Initiator]:[PC] using the samevolume of DMA as that of the monomer added.

Example 8: Additional Radical Addition and Coupling Reactions

To determine if the strongly reducing dihydrophenazine 5 could directlyreduce CF₃I (peak reduction potential (Ep) of −1.52V vs. SCE on glassycarbon), thereby generating CF₃C for the trifluoromethylation ofunsaturated substrates (FIG. 38). Using white LED irradiation of 3 (1 to5 mol %) in the presence of 1.5 equivalents of potassium formate(HCOOK), CF3 was successfully installed onto five-membered heteroarenes(indoles, pyrroles), arenes, and alkenes at moderate to excellent yields(42% to 98%). For alkenes, the presence of HCOOK base affords thesubstitution product, while the absence of HCOOK favors the additionproduct. The reduction of CF₃CF₂I was also accomplished, generatingCF₃CF₂C for substitution onto indoles and alkenes. Thetrifluoromethylation of 3-methylindole was achieved with similar yieldusing natural sunlight. The substitution reaction between10-undecene-1-ol and CF3I could be performed using lower catalystloading (0.25 mol %, 69% yield) or on a larger 10 mmol scale (1.74 gproduct, 73% yield) while maintaining good yields.

Dual catalytic approaches integrating photoredox catalysis using iridiumPCs and nickel-catalyzed cross-coupling reactions have enabled access toC—O, C—S, C—N, and various C—C bond forming reactions. Incorporating thephotoredox cycle introduces redox or energy-transfer mechanisms with thenickel complexes to complete otherwise demanding catalytic cycles.Cross-coupling reactions have traditionally been catalyzed by palladiumcomplexes at elevated temperatures to construct such critical bonds.

A dual photoredox/nickel catalytic approach employing 0.02 mol % ofpolypyridyl iridium PC [Ir{dF(CF)₃ppy}₂(dtbbpy)]PF₆[dF(CF₃)ppy=₂-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine;dtbbpy=4,4′-ditertbutyl-2,2′-bipyridine] in conjunction with NiBr₂.glymecould efficiently catalyze C—N bond formation under mild reactionconditions. At similar reaction conditions, albeit using a highercatalyst loading (0.4 mol %), PC 5 or PC 7 in combination withNiBr₂.glyme successfully catalyzed C—N coupling reactions at good toexcellent yields (68% to 96%, FIG. 39). The scope of amines includedboth primary (aniline, furfurylamine, and propylamine) and secondaryamines (pyrrolidine and morpholine) and were effectively coupled withelectron-rich, electron-poor, and heter-ocyclic aryl bromides. Forsecondary amines, both PC 5 and 7 catalyzed C—N bond formations,although PC 5 generally gave slightly higher yields. Whilst PC 5 wasunsuccessful in effecting C—N cross-coupling involving primary amines,PC 4 proved to be effective to couple primary amines in high yields.

In regards to C—S cross-coupling, the dual photoredox/nickel catalysiswith 2 mol % [Ir{dF(CF)₃ppy}₂(dtbbpy)]PF₆ and NiCl₂.glyme produced C—Scoupled products under mild conditions. At analogous reactionconditions, phenoxazine PC 7 achieved C—S cross-couplings at good toexcellent yields (64% to 98%, FIG. 40), but proved efficient at a muchlower PC loading of 0.2 mol %. Aryl thiol (thiophenol), alkyl thiol(4-methoxybenzyl mercaptan, 1-octanethiol and cyclohexanethiol) andcysteine (N-(tert-butoxycarbonyl)-1-cysteine methyl ester) successfullycoupled with a variety of aryl bromides. Aryl bromide coupling partnerswere successfully incorporated with organic PC 4, which were shown to beinactive when using [Ir{dF(CF)₃ppy}₂(dtbbpy)]PF₆. PC 5 was unsuccessfulin C—S coupling reactions, presumably due to its stable radical cation(E0 ox=0.21 V vs. SCE) being unable to generate a thiol radical involvedin the coupling reaction.

These photoredox/nickel C—N and C—S cross-coupling reactions could bedriven by natural sunlight to obtain similarly high yield. Furthermore,both the C—N and C—S couplings could be performed on a larger 10 mmolscale reaction for C—N (1.22 g, 53% yield) and C—S (2.92 g, 98% yield)couplings. In these scaled reactions, C—S coupling maintained the highyield, while C—N coupling suffered a 30% drop in yield. This lower yieldwas attributed to limited light penetration owing to the opaque solutionmixture compounded by the lower molar absorptivity of PC 5.

The disclosures of each and every patent, patent application, andpublication cited herein are hereby incorporated herein by reference intheir entirety.

While the invention has been disclosed with reference to specificembodiments, it is apparent that other embodiments and variations ofthis invention may be devised by others skilled in the art withoutdeparting from the true spirit and scope of the invention. The appendedclaims are intended to be construed to include all such embodiments andequivalent variations.

What is claimed is:
 1. A compound, or a salt or solvate thereof,selected from the group consisting of:

wherein: each occurrence of R is independently selected from the groupconsisting of H, C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substitutedphenyl, —OH, —O(C₁-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O) (C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)2(phenyl), each occurrence of R₁ isindependently selected from the group consisting of phenyl, 1-naphthyl,and 2-naphthyl, each of which is independently substituted with at leastone R; each occurrence of R₂ and R₃ is independently selected from thegroup consisting of phenyl and 4-phenyl-phenyl, each of which isindependently substituted with at least one R; and each occurrence ofR₄, R₅ R₆, and R₇ is independently selected from the group consisting ofphenyl, 4-phenyl-phenyl, 1-naphthyl, 2-naphthyl, triphenylamino,phenanthrenyl, and pyrenyl, each of which is independently substitutedwith at least one R, wherein: if the compound is

then each occurrence of R is independently selected from the groupconsisting of C₂-C₆ alkyl, C₁-C₆ haloalkyl, substituted phenyl, —O(C₂-C₆alkyl), —NO₂, —C(═O)OH, —C(═O)O(C₂-C₆ alkyl), —C(═O)O-phenyl,—C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂, —S(O)₂NH(C₁-C₆ alkyl),—S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆ alkyl), —S(O)(C₁-C₆ alkyl),—S(O)₂(C₁-C₆ alkyl), —S(phenyl), —S(O)(phenyl), and —S(O)₂(phenyl); ifthe compound is

then each occurrence of R is independently selected from the groupconsisting of C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substitutedphenyl, —OH, —O(C₂-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl); if the compound is

then each occurrence of R₁ is independently selected from the groupconsisting of 1-naphthyl and 2-naphthyl, each of which is independentlysubstituted with at least one R.
 2. The compound of claim 1, wherein R₁is 1-naphthyl or R₁ is phenyl substituted by at least one substituentselected from the group consisting of CF₃ and C(═O)OH.
 3. The compoundof claim 2, wherein the compound is selected from the group consistingof:


4. The compound of claim 1, having the structure of

wherein R₁ is independently selected from the group consisting of1-naphthyl and 2-naphthyl, each of which is independently substitutedwith at least one R; and R₂ and R₃ are independently selected from thegroup consisting of phenyl and 4-phenyl-phenyl, each of which isindependently substituted with at least one R.
 5. The compound of claim1, wherein if the compound is

wherein R₂ and R₃ are independently selected from the group consistingof phenyl and 4-phenyl-phenyl, each of which is independentlysubstituted with at least one R,

then R₁ is 1-naphthyl.
 6. The compound of claim 5, having the structure:


7. The compound of claim 1, wherein the compound has the structure:

wherein each occurrence of R₁ is independently selected from the groupconsisting of phenyl, 1-naphthyl, and 2-naphthyl, each of which isindependently substituted with at least one R; each occurrence of R₂ andR₃ is independently selected from the group consisting of phenyl and4-phenyl-phenyl, each of which is independently substituted with atleast one R; and each occurrence of R₄, R₅ R₆, and R₇ is independentlyselected from the group consisting of phenyl, 4-phenyl-phenyl,1-naphthyl, 2-naphthyl, triphenylamino, phenanthrenyl, and pyrenyl, eachof which is independently substituted with at least one R; and eachoccurrence of R is independently selected from the group consisting ofC₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substituted phenyl, —OH,—O(C₂-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl).
 8. The compound of claim 7, whereinthe compound is


9. A compound, or a salt or solvate thereof, having a structure selectedfrom the group consisting of:

wherein: each occurrence of R is independently selected from the groupconsisting of H, C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substitutedphenyl, —OH, —O(C₁-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O) (C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl), each occurrence of R₁ isindependently selected from the group consisting of phenyl, 1-naphthyl,and 2-naphthyl, each of which is independently substituted with at leastone R; each occurrence of R₂ and R₃ is independently selected from thegroup consisting of phenyl and 4-phenyl-phenyl, each of which isindependently substituted with at least one R; and each occurrence ofR₄, R₅ R₆, and R₇ is independently selected from the group consisting ofphenyl, 4-phenyl-phenyl, 1-naphthyl, 2-naphthyl, triphenylamino,phenanthrenyl, and pyrenyl, each of which is independently substitutedwith at least one R.
 10. The compound of claim 9, having the structure

wherein each occurrence of R₁ is independently selected from the groupconsisting of phenyl, 1-naphthyl, and 2-naphthyl, each of which isindependently substituted with at least one R; each occurrence of R₂ andR₃ is independently selected from the group consisting of phenyl and4-phenyl-phenyl, each of which is independently substituted with atleast one R.
 11. The compound of claim 9, having the structure of:

wherein R₁ is independently selected from the group consisting ofphenyl, 1-naphthyl, and 2-naphthyl, each of which is independentlysubstituted with at least one R.
 12. A compound, or a salt or solvatethereof, having a structure selected from the group consisting of:

wherein R is independently selected from the group consisting of H,C₁-C₆ alkyl, C₁-C₆ haloalkyl, optionally substituted phenyl, —OH,—O(C₁-C₆ alkyl), —NO₂, —CN, —C(═O)OH, —C(═O)O(C₁-C₆ alkyl),—C(═O)O-phenyl, —C(═O)(C₁-C₆ alkyl), —C(═O)-phenyl, —S(O)₂NH₂,—S(O)₂NH(C₁-C₆ alkyl), —S(O)₂N(C₁-C₆ alkyl)(C₁-C₆ alkyl), —S(C₁-C₆alkyl), —S(O)(C₁-C₆ alkyl), —S(O)₂(C₁-C₆ alkyl), —S(phenyl),—S(O)(phenyl), and —S(O)₂(phenyl).